texts: Arduino Analog Input example clarification

texts:
First of all I'm total nub in electronics.

Recently I got an Arduino Nano. Now I'm trying to understand why there is no potentiometer nominal at http://arduino.cc/en/Tutorial/ReadAnalogVoltage example and how variation of this nominal would affect Analog input readings.

Also why at http://arduino.cc/en/Tutorial/AnalogReadSerial example they picked 10k potentiometer, what would be different with 200k potentiometer.

Thanks!


texts: Circuit wanted to run 12VDC LEDs from Low Voltage landscape circuit

texts: I have some 1w 12VDC Weatherproof LEDs that I'd like to use for lighting my pond, where I have an existing 12VAC lighting circuit.   I understand that the voltage from the landscape light circuit could run as high as 14V, although I haven't measured it yet.   What can I use (that I could reasonably make weatherproof) that would allow me to run 3 (perhaps 4) of these from this supply?


texts: Voltage regulator reference capacitor values

texts:
I've been looking at the LM78xx.

simulate this circuit – Schematic created using CircuitLab

The notes state:

So, input and output must be referenced to ground. C1 removes power line noise/ ripple and C0 improves switching stability.

Why was .33uF selected for the input capacitor and .1uF selected for the output capacitor?


texts:
I am wondering how simulator (LTspice, Cadence,...) compute DC operating point of MOSFET in DC analysis.
I know that in DC analysis, capacitors are open and inductors are short.
With MOSFET how is it modelled in DC analysis?


texts:
I'm confused about the Vrms value of a clipped rectified sine:

The reason it's clipped and distorted, is because it's the output from a tiny transformer (0.7W), and the filter bank charges at the peaks of the waveform, pulling down the voltage.

Anyway, it measures as 3.88V peak, yet only has 1.39V RMS. I don't understand that. If it were a sine with the same peak of 3.88V, Vrms would be 2.74V. If anything, I expect Vrms to be higher than that (like driving an amplifier into clipping increases power to the load).

Can this really be the correct Vrms value?

The scope itself seems to behave OK; sines, quares, triangles with and without DC offset measure correctly. Edit: actually, it doesn't... It doesn't include DC offset in the Vrms value.


texts: Parallel prefix adder cells in Negabinary

texts:
I'm trying to design a parallel prefix adder for a negabinary based adder. Negabinary is base \$-2\$ instead of the familiar base \$2\$ binary. Each 1 bit adder generates a sum and two (instead of one in binary) carries that go to the next adder.

To make the adder faster, I want to use a parallel prefix structure, like the Ladner-Fischer structure given below. I'm familiar with the functionality of the purple cell in the binary system, but I'm unsure how I could get the same functionality in the negabinary system.

The reason I'm doing this is just for fun, I haven't found any uses for negabinary yet.

Formulas for calculating the sum and carries:

\$s_i = a_i \oplus b_i \oplus (c_i^+ + c_i^-) \$

\$ c_{i+1}^+ = \overline{a_i}\overline{b_i}\overline{c_i^+}c_i^- \$

\$ c_{i+1}^- = a_ib_i\overline{c_i^-}+a_i c_i^+ \overline{c_i^-}+b_i c_i^+ \overline{c_i^-} \$

Ladner-fischer carry tree structure:

If anything is unclear, please don't hesitate to ask.


texts:
So I'm having this darlington pair here

I'm doing DC analysis of this darlington pair

Can anyone explain why is R2 is 6.58, shouldn't it be aprx 7.39?


texts: How to measure the tacho signal of a server fan 4-pin connector?

texts:
I'm trying to readout the tacho signal of a server fan with a 4-pin server connector. The fan is powered with a power supply connected to mains voltage (I'm sitting in germany means ~230V, ~50Hz). That the signal you want to measure is not superimposed with noise from the mains voltage you have to connect the ground reference from the oscilloscope properly.
I connected the oscilloscope needle to the tacho signal and connected the needles ground to the ground connector of the power supply. However the signal I measure ist still superimposed. (BTW: I've not used an oscilloscope for the last 5 years or so.)


texts: Locating mobiles/UE by base stations in a cellular system

texts:
After understanding a bit about how actual cellular systems function, I realized that identifying the mobile/UE location is key in assigning the UE to correct base station and thus to guarantee a reliable network. For this , cellular systems make use of RSSI ( Received Signal Strength Indication) and assosciated statistics.But, in reality this is less useful due to the existence of Non LOS paths and other factors.

My question is why can't the UE share its GPS coordinates with the base stations thus easing the whole process?


texts:
I am new here and I realy need your help. For diplome at the end of my studying I am making the audio amplifier module (power amplifier, preamplifier, tone control, power supply, linear regulator) all in one. A have almost everythink work yust can solve noisy hum in preamplifier (TL082) that is caused by DC power supply ripple. I put pi filter CRCRC (1k Ohm, 20 uF) before linear regulator to filter DC voltage from power amplifier and get pretty good symetrical voltage, but with 100 Hz noise at both voltages. How can I get rid of that 100 Hz ripple?

I am using LM337 and LM317 to voltage drop from 40 V to 18 V and that ripple also copy to the output of the linear regulator and causes hum in sound. Just for information, the power amplifier work great alone and also preamplifier work great with external DC power supply from professional power supply device.


texts: Is there a way, to turn off or set up to a button - the retracing of components(change of where the green lines connect), I came from old versions of EAGLE and there was a button for this, in proteus it does automatically all the time, but sometimes it is buggy.


texts:
To make it easier to read a waveform in the testbench, I want to use a signal/variable that is of string type. Basically e.g when I am reading address 0x03 from an SPI device, the string shall say that in words until the SPI transfer is complete.

This will make it easier to read the wave output.

Problems:

1) String variable/signal must be given bounds when it is created. Unlike C++ it does not seem to internally expand/contract to fit what is assigned to it at run-time. This should be possible for an aggregate.

2) Cannot use (others=>'') notation with string type even though it is supposed to be an array.

3) Sometimes I have a string returned from a different function that needs to be concatenated with the msg in the testbench. If I have to enter bounds for the string when I assign it value, this will become impossible.

Is there a way to use a string without assigning bounds in VHDL? Atleast can I assign value to a string such that if my assigned string is less than max bound, the rest of the string shall be set to space characters automatically?


texts: Impact of PCB revisions on its embedded software

texts:
Over the past couple of years we have done some minor revisions to our PCB, including

Different component selection (resistors / caps / ...) based on availability / price (while still taking into account their original characteristics)
Components layout on the PCB
Trace widths / lenghts (as a result of the layout)

What we've often found is that although these changes shouldn't really impact the embedded software, we still needed to tweak our software after each of those revisions.

Some hardware revisions brought instability with them that only showed up after days / weeks / months (ex: the inability to power toggle a certain component on the board)

We needed to tweak high/low sequences, serial line timeouts

The big poblem is that these issue don't show up immediately, but sometimes take weeks/months before they start popping up, making it difficult to perform corrective action (especially if one of the issues is the failure to power toggle the modem needed to perform a firmware update).

Are there any guidelines / best practices to eliminate that risk ? (some kind of stress testing procedure / things we need to take into account while doing such revisions ?


texts: Shuting down a motor using a limiting switch without using any microcontroller

texts:
I am designing a winch for carrying loads from a hole. I managed to put a boyer for alarm when the controller is not careful but I need a system to stop the motor from pulling when the bucket pass a certain distance from that boyer
I am using a three-phase motor, I need to use a limiting switch to stop the motor


texts:
In MOSFET datasheets they often lists parameters like VGS (ON) , Id (ON). Is VGS (ON) is the testing gate- source voltage that is being used (of course above threshold voltage) or it's a particular constant gate-source voltage which turns the MOSFET FULLY TURN ON? similarly what is this on state drain current?
As far as I know the degree of "on-ness" depends on the gate voltage, so what does it mean to have a "on" state drain current Id on? It is meaningless because the degree of "on-ness" depends on the user hence, different degree means different drain current. So, is on state drain current is the saturation drain current for a testing gate voltage?


texts: Problems related to Zener Diodes to determine the ratio of transformer

texts:
I am having a problem which is related to a circuit as shown below:

simulate this circuit – Schematic created using CircuitLab
I will give you more information about this circuit. V1 in this circuit is (220V/50Hz) and the transformer has no information about the ratio n1/n2. R1 is 200 Ohm as shown in the circuit but RL is unknown (Because I do not know how to clear the information of RL).
As operating, Uz1 = Uz2 = 4.25V and Iz1 = Iz2 = 2.5 mA.
My problem is to determine the ratio of transformer with these information. I found it really hard because I think there are not enough equations to calculate V2 (secondary voltage)


texts: How to fix a broken flap FCC connector flip-lock ZIF

texts:
While repairing a projector, I broke the flap holding the flat flex cable (FFC) in place. It's the type "flip-lock" and is ZIF (Zero Insertion Force) so without the flap in position, the connector doesn't work.

I've tried to contact some FFC connector manufacturers, but they were not able to help identify the part. Please mind that the only thing I know is that has 84 pins.

I read here and here that my challenge isn't easy, but I'm willing to give a try.

Do you have an idea of which manufacturer might produce such connectors?

Do you have an idea about how to fix it, rather than inserting a spacer under the FFC?

Thanks a lot.
I hope to have been enough clear and precise.


texts: Probability of receiving a fixed bit sequence in a binary symmetric channel

texts:
What is the probability of receiving 1111 irrespective of what was
transmitted?

\$0.1^4 + 0.9^4 = 0.6562 \$

I am not sure about my answer because I think in my solution I am excluding the probability of getting 1111 as a combination of the two (0 or 1). I only assumed that the 1111 is a result of 0 being transmitted \$0.1^4\$ or 1 \$0.9^4\$.

Can anyone clarify this point to me?


texts: LSM6DS0 accelerometer reading with HAL_I2C_Master

texts:
I try to read the accelerometer on LSM6DS0 with the HAL_I2C_Master. I am coding with truestudio c and my board is STM32l476RG. My slaveaddress is 1101011xb so D7/D6 for R/W. My accelerometer date can be read in the register from 28h to 2Dh. Infortunatly it don´t works i don´t know how can i show the data on my pc and to stored then.
Please i need your help.
Thanks

uint8_t*  i;
int main(void)
{
for(i= (0x28); i= (0x2D); i++)
{
 HAL_I2C_Master_Transmit(&hi2c1, 0xD6, i , 1, 100);

}

// receive the 2 x 8bit data into the receive buffer
HAL_I2C_Master_Receive(&hi2c1, 0xD7,(uint8_t*)0x2f , 6, 100);
HAL_Delay(100);


texts: Can voltage and current be stepped up and connected together

texts: Ok if a boost convertor is used to step up voltage, then a seperate buck convertor is used to step down, increasing the current, can these two be configured to utilize the high voltage on one output, then utilize the high current on the other output and connect the both together


texts: (LTSpice) Simulating a ideal transmission line

texts:
I have to simulate a ideal transmission line and I have drawn the following schematic in LTSpice IV.

When I run the command to simulate it works but only show a 10V steady value on the output in both start and end of transmission line. I'd like to see the transient values. Can anyone point me what I have done wrong?


texts: How does a Wilkinson power divider achieve isolation?

texts:
Say we have a Wilkinson power divider:

The explanation I've heard about how ports 2 and 3 are isolated is this: say there's a signal generator attached to port 2. This can take two paths to port 3: through the resistor, and through the two transmission lines. With the two transmission lines being a half wavelength, they invert the signal. So the non-inverted signal (through the resistor) and the inverted signal (through the transmission lines) is equal but opposite and so cancels.

That makes sense, but it's not enough to convince me that it actually works. For example, why split in half and not some other ratio which would not result in complete cancellation? And wouldn't port 1 have some significance to the operation?


texts: Is this a correct way to route current away from breadboard?

texts:
I've recently grown interested in electronics and robotics, so I wanted to move my contraption using a servo motor. A 555 chip creates a PWM signal for servo for positioning, and I control the servo with a variable resistor.

I'm sure it will be able to move my contraption with ease, but I'm not comfortable putting 3 A through the breadboard (which would happen if the servo stalled).

Would something like the following work?

I believe this would route power required by the servo around the breadboard so breadboard would only work with the current required for controlling the servo motor, for creating PWM.


texts: Several variations of the same chip, what does it mean?

texts:
When I look for ICs online, I often come across a list like this one.

For example, I just searched for the 4N35 optocoupler, and came up with a list:

4N35M
4N35SM
4N35SR2M
4N35SR2VM
4N35SVM
4N35TVM
4N35VM

And this is a relatively short list. Sometimes, differences are obvious (i.e. package type). But the aforementioned are all in DIP package. So is there some sort of a general convention that all manufacturers follow when naming these chips? I mean, how am I supposed to choose which one is right for me? Reading the datasheet searching for a minute difference each and every time can be tedious (sometimes it certainly helps), but I'm wondering if there is a fast way, based on the suffixes of the variants of a component, to tell how it differs from other members in its family.


texts: How to graduate from Arduino to using a microcontroller directly?

texts:
I've been working on an Arduino project. After I get everything working using the Arduino, I would like to move to a solution that does NOT use Arduino. That is, I would like to use a microcontroller without involving the Arduino board. This will allow a single board, no shield solution.

I know there are methods to make my own Arduino on a breadboard, but that's not really what I'm trying to do.

I'm not really how sure how to do this.

Unless there is a better option, I'm leaning towards using the ATmega328, which is used by the Arduino. I understand that development tools are available free or at least not very expensive.

For the purpose of this question, assume I can get +5V to my circuit.

My first question is how to program the MCU. I believe there are two options:

Buy a programmer, program the MCU, and then place the chip in my circuit.
Design my circuit to include support for in-circuit programming.

I'm assuming that if I go with option #1, it's as simple as inserting a programmed chip in my circuit; I don't need anything else. Of course changing the software would be inconvenient.

But for option #2, I'm not sure what I need.  From the bit of reading I've done, I think I need a programming cable, and a connector on my board (what type?). Then I guess I (properly) wire the connector to certain pins on the ATmega.

Either way, I will need Atmel studio.

Second, other than the power supply, is there anything on the Arduino that I absolutely need? I guess maybe a reset switch?


texts: Thermocouple temperatures change drastically when my whole system is powered vs when just my arduino is powered

texts:
I apologize in advance if this should instead go in the Arduino stack exchange, but I feel it should be here.
I'm using this thermocouple / amplifier pair with my Arduino Uno.  I am trying to make my own version of Ben Heck's Solder Reflow Oven by modifying a black & decker toaster oven.  I have almost everything set up and working, the one thing I have left to do is get consistent readings from my thermocouple.
My system consists of the following:

-Line, neutral, and gnd go into a 24V power supply.  This goes to a 12v regulator and to the arduino.  The reason I use 24V is because I was unsure at the time what the largest voltage requirement would be in my subsystem.
-the arduino is controlling a 12V relay and receiving readings from the thermocouple.

When the relay is flipped and the oven coils are receiving current, my thermocouple readings drop by about 15-25 degrees C (this value kind bounces around, but is consistently less).  When I turn off the system and power the arduino via usb, my thermocouple reads a nice, consistent value (slowly decreasing as the oven cools).
So it would seem that the power required to heat the oven coils is in some way affecting the thermocouple, but I don't really know much about fixing these types of issues.
What could be causing this?
My only thoughts are either a) it's caused by sucking power away from the arduino because the oven requires so much power or b) since the coils operate at around 120V 10A they may be causing some sort of EMI issue, which I know literally nothing about fixing.
Can I get some insight as to what my problem may be and some suggestions on how to fix it?
edit:
here's a super simple diagrom showing the connections in the entire system

The relay, once flipped, connects the live line together, which is what turns on the oven.


texts: Controlling the turn on/off of a 380-440V high voltage water pump

texts:
I'd like to control the turn on/off of a NFw Series Centrifugal Water Pump 380-440V high voltage water pump using an Arduino.

I have searched for how control it, but I haven't found any ideas. Can you kindly give me a suggestion?


texts:
One can sometimes observe rectangle pads in the corners of some IC's footprints:

What are they for?


texts: I have to design a circuit that maximizes power to RL which is a resistance representing a speaker attached to the end of a LM741 op-amp. This is a non-inverting op amp in the circuit, and I just need a generalized explanation of what to do to get the maximum power to (or dissipated in) RL.


texts:
I am wondering if it is possible too hook up an oxygen concentrator in my car for longer than normal trips. My gf needs 10 to 15 liters but can maybe get away with 10 (1 machine) for a drive. The machine is 120volts almost 600 watts ( i believe it says 4.5A) and I usually run two machines in the house but for a drive for about 4 hours i can get away with 1 machine but don't have enough portable oxygen. Do you think i can add an inverter and batteries in my trunk to run the machine? if so i would need advice on installing it.
Thanks


texts: Single ended scope probes on equipment under test which ARE on an isolation transformer

texts:
I am using my company's new oscilloscope and I don't want to mess it up. I have searched all of the topics, but nothing tells me exactly what I want to know so I thought I would ask in case somebody had the same question.
The team designed a switch-mode power supply and an audio amplifier. I'm supposed to test both, but I am a little embarrassed that I don't know what will and what won't blow-up the DUT, the scope, or the probe. We have a normal 115VAC/60Hz outlets, powering the oscilloscope and the AC power supply. We also have an isolation transformer if I want to plug it directly into the wall. I am using a differential probe, but I only have one of them and need to look at 2 signals at the same time. I have lots of single ended probes.

Can I use a single probe anywhere if the equipment is on an
isolated outlet (we have isolated outlets on the front of our AC
supply).
If that doesn't work, can I put the DUT on the isolation transformer and then use the single ended probe anywhere?
If the DUT is on the isolation transformer, can I put the alligator clip anywhere I want? if I want to measure the high-side fet of a half-bridge LLC circuit, can I tie the ground clip to the switching net and it just behaves like a differential probe?
Is there any danger in using signal ended probes on the primary side of the high-frequency transformer in the LLC and the secondary side of the high-frequency transformer at the same time?

I appreciate any help you can help me to learn how to do this correctly!
Jeff
DEFAULT SET-UP

ALTERNATE SET-UP IF NEEDED


texts: unwanted time delay in latch-circuit with diode

texts:
I am trying to use the following circuit. It somehow does what I want, but I would like to
a) get rid of the time delay.
b) would like to understand, why the time delay gets that high (and also, why its getting higher, the longer its functioning without a reset (up to 15seconds))
Short explanation for the circuit: My SW1 is just me giving one 5V pulse to the circuit.
This leads to a latch, my Q1 is switching, thats fine.
The reset isnt a pulse, I am putting the wire to the ground and I am leaving it there. But getting the voltage down needs to much time, what can I do ?

simulate this circuit – Schematic created using CircuitLab


texts: Solder various parts of broken wire in a fan coil

texts:
So, in a not that careful attempt to open holes on a fan to get the air to go through it more (it heated up a bit too much compared to another fan in the house), I broke the coil wire in some points...
Is it possible to solder it back without insulating? Or this would reduce the impedance and then have some bad consequence on the fan? Or forgetting the impedance, maybe the electrons would just stop going through parts of the coil ("easier" if there's a smaller path) and the fan wouldn't work decently, maybe even slower (because of the shorter path of electrons) or something?
If I do have to insulate the wire after soldering, could it be with electrical tape? Or it needs some thing more advanced? (I've been learning more deeply about soldering because I only knew soldering iron + tin = stuff soldered 2 weeks ago, so I don't have advanced things, but I can try to buy the needed thing if the ones I have are not enough.)
Actually... Can it be done at all? Bellow goes a picture of the broken wire in some points. I haven't turned on the fan since I broke them, so no idea if I should and see what happens? Because it's the same wire, just touching on itself in some points, so I guess it shouldn't short-circuit it?

PS: I know I could just buy another one, but why not learn a bit more and try to fix this one haha (again, if it can actually be done, as broken on one point only it would be easier with the insulation since all the rest is insulated, but broken on various points ones bellow the others I guess it may be harder).
Thanks in advance for any help! Also hopefully this is a good place to ask this kind of question... I'm sorry if it's not.


texts: Should it be expected that some shielded wire is not good at data transmission?

texts:
I have recently purchased a reel of this specification screened wire from RS Components to use in I2C communications, expecting it to be very well suited to purpose. I am running at approximately 400 kHz clock on the wire and did not think for a second that the choice of cable might limit the speed I could run at. However on oscilloscope inspection, the bus signals are extremely dulled by the connection of a 3m length of this wire.

Is the problem with the I2C master not having a sufficient pullup resistor say, or is the wire genuinely at fault? Is there a significantly better wire specification I could use for this application?

Further Information:

It is true this wire is listed as 95pF/m. I have found a different spec of wire (for microphone use) that seems potentially impossible based on the physics discussed, but here it is, 55-105pF/km.


texts:
For a project I have a digital thermometer which outputs a DC voltage of 100mV at 20 degrees C and 250mV at 50 degrees C, which is the range we're interested in.
We're putting that into an Arduino via and ADC, which can handle voltages of 0-5V.
To make best use of the resolution of the ADC I'd like to reduce that 100mV-250mV to 0 to 5V, but although I can find circuits for the gain easily enough, I can't seem to figure out the initial reduction of 100mV.


texts: Simple circuit- Diode and the output voltage

texts: I have found the current right but I thought 22V-2.2k(4.84mA)-0.7 would be equal to V0 (or 2.2k(4.84mA), voltage from lower branch- both are equal and so no inconsistency), why is my logic wrong and where did 1.2k come from?


texts: Picking a camera to use with an Arduino uno. (Or freetronics eleven)

texts:
Right, so after browsing my 'local' online computer shop with 'nary a basic idea of what I can to do I've decided I'd turn to people who knew more about electronics than me.

My plan is to hook a couple of motors and a basic camera to my Eleven (which apparently functions just like a Uno) and when the computer sends a command to the Eleven it snaps a picture and pipes it back to the PC.

My question to you fellows, is would that be possible, or do I have to add in more memory so it can buffer the image first? What camera should I use? I've seen multiple suggestions online and while I know the simplest solution would be to use a separate camera I'm looking for a more elegant and portable answer.


texts: Two level LED strip on different voltage with separate switches

texts:
I'd like to have an LED strip with two levels of lighting, one triggered by motion sensor (7v because I've tested the meter long smd3528 strip and it operates at low steady level at 7v), and the other 5v to boost up to 12v on a switch (connected to pantry door) for the strip giving me full light.

The reason I'd prefer not to use a dimmer is that I'm using it in my kitchen and when working there don't want to have to wash and dry hands to operate a dimmer. Pantry (like a closet in my kitchen where food and spices stored) door is usually open when I'm cooking so a switch on that for the additional voltage would be convenient.

At other times, not cooking, just need the dim light for getting a glass of water type action.

I thought of splitting the strip, having two smaller ones both at 12v, but kitchen is tight and full of angles and the longer one gives gentler, ambient lighting, less shadows.

I realize this is easy and cheap enough to test for myself but thought I'd ask while waiting for parts to arrive and ask (if successful) if there's a better design for more general applications? Also, would it matter if the 5v supply were added at the other end of the strip rather than joining the 7v line prior to the strip? Do I need that diode or more than that?

(there are two diagrams (I did my best without knowing legit symbology) because I know real world electricity is strange and if wiring both buck converters to the 12v and then rejoining would create a problem, plus if I opened the door during the day when motion sensor was not operating (it's a light sensor too) then I'd be putting 5v through strip and maybe that wouldn't be good for led strip)

Update: Just thought of putting the motion switch before the first buck converter so it controls the whole 12v supply and I wouldn't have to worry about 5v trying to light the strip.

simulate this circuit – Schematic created using CircuitLab


texts: Can the COM and NO terminals of a mechanical relay be used interchangeably?

texts:
I have a 240v 30a relay and for layout purposes it may be helpful to orient the relay such that the NO contact is where I’d like the COM contact to be.

As it is a NO relay can I simply connect my input power to the NO terminal and the output to the com? Is there something I’m missing that would make this an unwise idea?

This is the relay I'm using,T9AS1D12-12,  but I'm actually interested in the answer in a more general sense, if there are typical reasons why one could not reverse the terminals.


texts: Why PWM does not regulate voltage across MOSFET?

texts:
I am trying to control a DC voltage using pulse width modulation (PWM) and an N-channel MOSFET. The way I have set up the circuit is as follows:

However, instead of the motor I have a 100K resistor, in parallel with a 100microfarad (25V) capacitor in order to smooth out the voltage. I am measuring the voltage across this resistor to check if it is being regulated or not:

I am powering the load from the same Arduino (for the time being. I will power it with an external battery once I get PWM working). I have the following code running on the Arduino:
int pwmPin = 3; // connected to the MOSFET's gate
int val = 128;  // set between 0 and 255

void setup() {
   pinMode(pwmPin, OUTPUT);
}

void loop() {
   analogWrite(pwmPin, val);
}

However no matter what I set the value to, I see the output voltage to be the same value of 4.99V instead of being proportional to the duty cycle. This changes as I get very close to 0 (when val=10, V_out = 4.33V and when val=0, V_out = 0V).
Why is this happening? Is the transistor not fast enough? Is the capacitor not big enough? What am I doing wrong? Below are the datasheets for the components:
Transistor (TO-220)
Diode
Sorry if the post has become wordy. I have been downvoted in the past for not including enough details with my post (because I wanted to be concise) and now I am being cautious.
Any help is much appreciated!
Edit: Please disregard the values on the diagram. I have wired my circuit as shown but for the values, as explained in my post I am using the Arduino to power the load. Meaning that the positive pin of the load is connected to Arduino's 5V and the black line in the diagram is connected to the ground of the Arduino. (I did not make the diagram myself and I was myself confused about the 0-60V+ and 0-60- notation, I'm assuming it means the 10K resistor was chosen such that such a range of values would not damage the circuit) I have also included the datasheet to the specific transistor I am using. Thank you for the answers so far.


texts: I need help understanding constant voltage model for diode

texts:
So I'm confused about the constant voltage model (which assumes diode has .7 volt drop).

In the pic below, I'm confused about the third case. What if the voltage source has voltage less than .7 V but the diode is in forward bias? Does that mean it's open circuit and hence the voltage drop across the diode will equal that of the voltage source? (In the last two cases---in the circuits to the right--I just made up numbers to illustrate the concept)


texts: Understanding + modelling passive filter (crossover) circuits: Component position and effect

texts:
I'm trying to learn more about how passive filters work by modelling a speaker crossover (using Qucs), and as a starting point I'm using a crossover from a speaker I've built as an example, since I'm familiar with it.

What has me really scratching my head about this circuit is that unlike pretty much every example crossover and filter diagram I've seen online and in textbooks, the series components are all placed between the negative terminal of the driver and Ground instead of between Vin and the positive terminal.

Taking the woofer circuit as the simplest example since the driver isn't inverted, this means that Vin = Vout for any input V, doesn't it? So a couple questions:

1) Am I missing something obvious here? Can the diagram be flipped or rewritten in an equivalent (more standard) way and I'm just not seeing it?

2) If not, how does this filter work with this layout? And where would you place a probe to measure Vout in a sensible way?

3) The inversion of the tweeter makes this even more confusing to me, how does that fit in? (or is it unrelated?)

Thanks in advance for any tips to help understand this!


texts:
I'm new here and wonder if you could help me out.

I'm trying to build a Lipo warning/cutout circuit for four lipocells.

The idea is to have a bicolor led showing green above 14V, orange between 14-13.5V, flashing red belov 13.5V and red below 12.5V also switching off the load.

I built and programmed the circuit and it works fine using no load, but with a load drawing about 5A the output from the 7805 rises to about 5.5V offsetting the programmed levels (although in the right direction) but perhaps destroying the cpu.

My question is what did I do wrong when designing this circuit?
Why is the output from the 7805 changing when applying a load?


texts: SPI clock - slow frequency but fast rise time issue with waveforms

texts:
Background on the issue:

I currently have an SPI bus between an Atmel ATSAM3X8E and a Spansion FL164K flash memory chip.

SPI has always been super reliable for me in past projects, but this design is being very temperamental (the routing is far from ideal).  Some boards work fine, some have very occasional data loss in the SPI comms, some have nearly constant data loss.  The data loss that I refer to is most easily reproduced by constantly polling the ready flag during a ~50 second erase.  Mostly the busy response is 0x03 (0b00000011), but occasionally comes back as not busy - 0x00 (0b00000000).

Fortunately I can reproduce the fault on the bench, and fortunately I can also make the problem go away.  Unfortunately though, connecting a passive probe is one of the things that makes the issue go away, so I can't 'see' the fault.    And I'm not happy to call it fixed if I am not certain what I am actually fixing.

Circuit design info:

The SPI bus is routed to 3 things - SPI flash, SD card (which is not installed), and a basic 6 pin header
The red pad in the bottom right is the MCU (clk source), the stub that comes off immediately goes to an n-channel FET which drives an LED, the SOIC8 IC with the red pad is the SPI flash, the 6 pin header above it is unpopulated, and the blue pad at the left side at of the trace is an unpopulated SD card connector.
The actual distance from the MCU to the SPI flash is ~35mm, and the SPI flash to the SD card pad is ~30mm.  The stub to the FET is ~25mm and the stub to the header is ~8mm.
The layout is far from ideal, and I understand that, but the intention was to only run it at <1MHz, so I incorrectly assumed that transmission line theory/terminations/reflections were not needed.

Ways that I can already prevent the problem:

Add a ceramic capacitor from CLK to ground in the 6 pin header (I have tried values from 18p to 330p).  All of them slow the rise time, and the problem doesn't persist
Add a 1k resistor from CLK to ground.
Attach a scope probe
Touch the CLK line with my finger

So basically any way of adding capacitance or loading to the circuit seems to make the reads 100% reliable.

Waveforms (taken with a Rigol DS1054Z with the 100MHz option, and a 150MHz passive probe using a ground spring):

Note: a scope probe is obviously connected for all these (which stops the problem happening).  The waveforms we see here are not actually bad enough to cause the problem, but hopefully give an idea of what could be bad enough to cause the issue when the capacitance of the probe is removed.

Note 2: These shots were taken at a 5MHz clock rate, but the problem seems to manifest at anywhere from 100kHz to 20MHz.

On initial inspection the clock signal looks good (albeit very fast ~8ns rise time).

But a closeup shows a bit of a step halfway up

And at the fastest time scale, this is what I see.

Finally, the questions

Is a step in the rising waveform typical of transmission line reflections or something else?
Given that the read issue occurs regardless of clock frequency, I assume that the rise time (8ns with probe attached) must be combining with the poor routing to cause the data issues.  But don't fast rise times cause ringing, not a stepped waveform?  Is it common for a scope probe to dampen ringing that otherwise occurs?
Looking at the waveform, what actually happens inside the slave to cause an issue? (the SPI slave double clocks because of that step? or the SPI flash isn't getting it's specified 0.1v/ns slew rate? or something else that I don't understand yet?)
Finally, what else could I do to try to assess the signal without loading (fixing) the signal, short of spending $$$ on an active probe that may or may not make a difference?

As you can tell, higher frequency theory is not my area of expertise, so I appreciate anyone's experiences in this area.


texts: What's the reference dB level in spectrum analyser

texts:
I am using a Spectrum analyser.

Measuring the 248kHz buck switching frequency and its harmonics in my board.
I have set the frequency range from 200kHz and 1MHz. Using a near field H-Probe

When I give peak search on the spectrum analyser, I get a peak at the 248kHz freq with amplitude of 40dB and when I change the amplitude level in voltage, I get -14dBmV.

I also get other harmonics too.

I just want to understand two things :

I know the dB is just the ratio of two quantities (power or voltage). But when I get 40dB and -14dBmV, what is the reference level that is taken by the spectrum analyser which it compares with the output power? I assume the spectrum analyser takes a reference voltage or power level and compares it with my board output level and then only it provides the value of 40dB and -14dBmV. Am I correct?
What does the +ve and -ve dB value signify in electrical terms?

Please understand that I am just starting the learn the uses and the operation of spectrum analyser. Would be glad if someone could help with the answers in simpler terms.

Thank you

Edit :

Please find the attached image from this AppNote from Keysight

The images shows a reference level set at the top. How is this value chosen and on what basis?


texts:
I have built an automatic water tank using the circuit given below:

But this circuit was working well for 2 days. But after that, it triggers falsely. When a fan in another room is switched on, this circuit trigger the relay and motor will turn on.

I think this is due to AC noise. I was using 12v AC to DC converter supply, i.e, 12DC adapter.

Can anyone help me to avoid this situation?


texts: I was just curious. Can one parallel Linear Regulators, LDOs or Switching Power Supply ICs in order to increase total possible power output? By parallel I mean tie Vin to the same rail and Vout to the same rail and duplicate any supporting circuitry (feedback networks, caps etc.).


texts: What kind of power connector is this? Attached to Adafruit 32x64 Matrix

texts:
I've been searching on Digikey and Mouser for this connector, but haven't figured it out. It's the same one that's on Adafruit's 64x32 LED matrix.

It's spacing is greater than 2.54 mm, so maybe around 2.9 or 3 mm.

Thank you


texts:
I'm doing my homework for digital logic in logisim. I need to make function solver for this function: f(x,y) = 6*y-8+x in 4bit arithmetic.
Here is my solution but it is not working for some inputs. I don't know where I failed. I will be thankful if you can help me somehow :)
Thanks

Solution:

Edit: it is working, for example for 0000 for X, and 0101 for Y, but it is not working for 0000 and 1101. I need to get solution for function above


texts:
I am trying to send data through serial from a 3.3v Arduino to a 5v Arduino.  I assume I can't just connect the 3.3v tx to the 5v rx because, when I program the 5v one I am assuming it will send 5v signals to the 3.3v Arduino's tx pin, potentially damaging it.

I don't want to use Software Serial because I want to take advantage of the Arduino's hardware UART buffer.

If I use a diode, I am concerned that the voltage drop will cause the 3.3v signal to not be picked up by the Arduino rx (I have heard that >=3v registers as high).  I have heard that Schottky diodes have a low voltage drop so could I use one of those with a rated drop of <0.3v?  Or is there a better way to get around this issue?


texts: Primary and secondary fuse size for a transformer

texts: I have a 220V AC to 24V AC transformer rated at 2Amps. What size of Primary and Secondary fuse should I use?


texts: Finding out the accuracy of the current probe's measurement

texts:
As part of power supply testing we are measuring the current profiles of various regulators.

Startup profiles includes current bursts with different current amplitudes and widths.

i want to understand the accuracy of the current probe*(MINIMUM CURRENT WHICH CAN BE MEASURED ACCURATELY UPTO 1% to 3%)* in measuring currents.

For example in my case,
I have TCP0030A current probe from Tek-

it has 2 ranges 5A and 30A.

1. whether in both ranges the accuracy differs or same

It has different specifications like

DC gain accuracy <3%(1% typical) - i am not sure what is this exactly?

Displayed RMS noise <75uArms

1mA sensitivity- Is this directly relates to Minimum current can be measured with this probe

If i want to find the accuracy of the measurement, how i can derive error from all above error sources.


texts:
I am trying to make an electric go-kart. I am new to the forum, so I may be missing some information but any help is greatly appreciated. After doing some math and discussing with friends I found the following with the given information. I have 4, 24V 14A motors, all connected to a read drive axle. I have 2 pairs of motors on each side of the drive axle. The motors have an 11 tooth sprocket that is chained to a 68 tooth sprocket that is connected to the drive axle. I currently have 2, 12V 7Amp 20 hour lead-acid batteries, which provide my 24V. Each pair of motors is connected in parallel to ensure they both get the 24V. However, the motors do not spin, even when there is no load (The wheels aren't contacting the ground). I believe that this may be because the motors do not have enough amps, only receiving 7 Amps of the 14 Amps from the batteries, because there are 2 motors in each pair. My main goal is to get the kart moving. I weigh about 130lbs, and the kart is likely around 30lbs. Would getting a battery/batteries with move amps (28A) allow the motors to run properly? Any advice is really appreciated.
All the information I know
Each motor is a DC motor that needs 14A and 24V
The motor has a sprocket of 11 teeth
The Watts of each motor is 250
The motors are rated to have an RPM of 2750 or around 45.83Hz
The drive axle has a sprocket of 68 teeth.
The 68 toothe sprocket is 5.5"
The wheel diameter is 10"
If my math is correct, given the ratio of the motors to drive shaft. Each motor produces 5.45Nm of torque, and after the sprockets, the torque is 33.69Nm. I don't know what impact the 4 motors would have on the torque, nor do I know what the torque is for each side. I really just want this kart to move.
Would removing motors allow my vehicle to move? I think that my power supply does not provide enough amperage to my motors. Would having 1 or 2 motors be better in this situation?


texts: SystemVerilog: Sensitivity list of always_comb

texts:
It seems to me that always_comb is not sensitive to variables assigned in the block itself. For example, the following block:

always_comb begin
    a = b;
    b = c;
end

seems to be only sensitive to c (so whenever c changes, b gets the value of c, and a gets the previous value of b) in simulation. If I synthesize this, it works as expected (a, b and c always have the same value).

Is there any reason always_comb, which is supposed to simulate combinational logic, behaves "incorrectly" in simulation?


texts: Do LEDs (of the same type) in parallel consume different current?

texts:
In a part of my circuit, there will be three LEDs (of the same type) in parallel. Is it true that they will not automatically get the same current and have the same brightness?
Somewhere I read about that.
The LEDs are: UV

Voltage Typ. 3,4V - Max. 4,0V
Current: 20mA Typ., 30mA Max

Up to now they do not have series resistors individually, but all three have one.
The whole thing will be an ultraviolet light show, regulated by a Raspberry Pi via 16 GPIOs, each of which will activate a mini panel of three LEDS.


texts:
I know that the number of KTL and KCL is related to the number of nodes \$N\$. For KCL there are \$N-1\$ equations while for the KTL there are \$L-(N-1)=L-N+1\$ equations. However I didn't understand how calculate \$L\$. Is it the number of elements in the circuit ? Is it the number of branches of the circuit ?

Consider the following example:

simulate this circuit – Schematic created using CircuitLab

The solution given for this circuit has 2 KTL equations and 1 KCL equation.
For the KCL is straightforward because there are only \$2\$ nodes so \$2-1=1\$ equation. For the KTL \$L-2+1=2 \Rightarrow L = 3\$. Why is that ? Should I consider only the branches entering one node ? That is \$(V1, R3)\$, \$(R2)\$ and \$(R4,R1,V2)\$ ?

Another way to figure out the number of KTL equations is by identifying the number of independent meshes. I can only see 2 meshes in this circuit but for a complex circuit how can get this value ?


texts: How to determine the voltage on the drain of a "hanging" PMOS

texts:
This is likely a simple question that has an equally simple answer. Below is the associated schematic.

The problem I'm having is identifying what state M2 is in, and what the voltage is at Va. I know that M1 is in cutoff (Vin = 0V < 1V). I also know that M2 will either be in triode or saturation, depending on the value of the drain voltage, Va. Furthermore, there's no current going into the gate of M3. So, The drain of M2 is basically left floating.

Unfortunately, my book neglects to mention how to determine the voltage on the drain/source in such situations.

My question, then, is how do I determine the voltage of Va? Also, what's the general rule of thumb when connections are left floating?

NOTE: My thought is that Va is around 10V, being that the MOSFET is on. That is, because the MOSFET can be modeled as a wire when it's on (broadly speaking), Va is really the same as node Vdd. At least that's my thought.

Any input is appreciated. And yes, this is homework.


texts: What are those black spots in these lead-free solder joints?

texts:
I have just changed to lead-free solder (I'm now using Chip Quik's "SMDSWLF.031, a Sn96.5/ Ag3.0/ Cu0.5 solder with 2.2% no-clean flux) but I'm not sure what I'm seeing when inspecting my boards.

The following pictures show an example: the first one was taken after soldering and I think the yellow residue around the joint is flux but I don't know what are those black spots on the solder; the second one was taken after cleaning the board with isopropyl alcohol and the yellow residue is gone but the black spots are still there.

My solder station is usually set between 350 and 375 Celsius (usually the later since the change to lead-free solder) but it seems the temperature settings does not make any difference on the appearance of the black spots.

What I see is that the black spots appears more frequently in larger pads. I wonder if it is because I left the soldering iron more time heating the solder and that burnt the flux.

When used leaded solder never saw those black spots (and the joints looked nicer). However, I cannot go back to use leaded solder (regulatory requirement).

So, my question is what is that black residue? And as secondary question: is that a sign of a bad joint or maybe bad soldering technique?

Additional information: most components I'm using have their leads tin-finished. The PCB pads are HASL-finished (lead-free).

Update:
I tested with PCBs from a different provider (suspecting something in the HASL finish of the PCB pads) and even tried bare copper prototype boards but the black spots were still there. I also tried cleaning the solder wire before soldering, because I don't use the solder wire from the original roll, but it was repackaged by hand in smaller plastic tubes (suspecting residues from the hands of the person doing the repackaging). I also tried to use a lower temperature, down to 275 Celcius (thanks to @metacollin 's for suggesting that), and changed the solder iron tip. Yet the black spots were still there.

Then I have rechecked the solder joints with a different light source. It is now evident those black spots are not residues but small depressions or pits in the solder surface. So now I'm inspecting the boards with a different lamp, because the one I used previously casts those hard shadows.

As a side note, lowering the temperature to 275-300 Celsius really improved the soldering. I'm surprised using a higher temperature actually made the melting of the lead-free solder slower. I guess flux was being burnt too fast and that made it worse with higher temperature.

I also contacted the solder manufacturer, they were the one suggesting to test with different PCBs to rule out something in the pad's finish.


texts: What are the typical uses for a soft-processor such as MicroBlaze?

texts:
I know that the FPGA-DSP combination is typically used for high-end power electronics/ultrasound/MRI/etc.  Is it possible for the soft-processor to fully replace the DSP even on lower-end FPGAs such as Spartan 3/6?

Added: What would be the reason for having multiple softcore processors in one FPGA?


texts: Does clock speed matter when recovering from I2C bus lock up?

texts: When there is I2C lock caused by slave device driving the SDA line low you need to manually generate a few clock signals by doing a simple bit banging on the SCL pin. I thought that this need to be done with the same frequency as the I2C communication was running before the lock up but it also works for me if I do a bit banging with a much lower frequency. Let's say I have I2C clock speed configured to be 100kHz, then I have a lock up and I generate a few clock signals with a frequency of 4kHz and immediately I2C is working fine again. Please explain if the frequency of bit banging does matter when unlocking I2C bus.


texts:
I was doing temperature testing of my product. Which had 230V input supply voltage Inside the product one SMPS module which convert 230Vac to 20Vdc. Again this 20Vdc converted to 5Vdc using DC to DC converter. I tested load regulation first at room temperature. I got following result

1) 5V  100mA =  5.010V,
2) 5V  300mA=   5.005V,
3) 5V  500mA=   4.998V,
4) 5V  750mA=   4.995V,
5) 5V  900mA=   4.990V

And when I test at -30C temperature

1) 5V  100mA =  5.004V,
2) 5V  300mA=   5.009V,
3) 5V  500mA=   5.012V,
4) 5V  750mA=   5.016V,
5) 5V  900mA=   5.019V

So at -30C temperature i observer voltage increase opposite what i observe at room temperature. Is this acceptable/Normal or this is so called temperature effect.


texts:
While reading this file on software hazards this slide says:

"No Back Branch in the Code"

I wonder what does it mean? Normally when we write code in C-language then we don't actually do branching explicitly as in the case of assembly language programming. Does it mean that the above design rule is only possible to follow at assembly level and not at the c-level programming?


texts: Replace 2 AA batteries with 5Vdc phone charger

texts: Is there a safe and easy way to replace 2 AA batteries that power 10 LEDs in parallel with an old 5Vdc 900mA phone charger?  I think the LEDs are standard 20mA ones.


texts:
I am developing a STM32H7 board which will be programmed via SWD.

I am curious, is there any reason why I should connect BOOT0 pin to GND via resistor and not directly to GND?

I won't be using the bootloader but can it happen that I accidentally disable the debug port from software and then can't program the MCU via SWD anymore and need to use bootloader mode by putting BOOT0 high?


texts: I am making a speaker with some neodymium magnets and about 3m of copper (insulated) cable. How would I configure this to make it loudest/best electromagnet?


texts:
Following through an example of designing an asynchronous circuit, Im stuck working out the state diagram. The design brief is:

  Design a circuit that has an input w and output z where z is ‘0’ if the number of previously applied pulses is even and z is ‘1’ if the number of previously applied pulses is odd.

The state diagram in the example looks like:

But I don't see how this matches to the design brief, because I don't understand how it know whether the last set of pulses were odd or even. So how is this the case?


texts: Which would be more applicable lmx or cc2564?

texts:
I'm looking for the difference's between a LMX family ic vs a CC256x family from TI and what you think would best fit my application. First my application is quite simple I'm using bluetooth to be able to write to the mcu EEPROM,and data log while the mcu is running.All transmitting over a UART connection.

The first major difference I can notice is the LMX requires less components for it to operate vs the CC256x. But that comes with a more pricey tag to it. Is this the only difference the LMX is a easier plug and play compared to the CC256x?Now im not limited to just these two products these were the two I felt would satisfy my application requirements.Any input is appreciated thanks

UPDATE:well typically once I post a question i find the answer. So the lmx has less components,and also has the bluetooth stack and profiles embedded in.While the cc256x family requires the mcu to contain the bluetooth stack and profiles.

So im going a complete opposite direction going to use the Toshiba TC35661SBG-203 has the stack and profiles embedded and the price is half compared to the lmx and will support my MCU without have to use one of TI ARM Cotex.Hope it helps someone


texts:
I have made a very simple inverting opamp amplifier to convert an output of 0-3.3V from a DAC to somewhere between -10 to +10V.

My reference (REF_1.65) is 3.3V/2 made simply by a 10k/10k divider of the 3.3V supply (buffered with 100nF cap). Both are not shown here.
So when going with DAC_REF from 0 to 3.3V, this voltage is going from positive to negative as expected.
However the output has more ripple than expected.
The output V_REF_X is used as a reference Voltage for an instrumentation amp. The point is, to roughly set the ReferenceVoltage (it does not have to be very exact) but stable, as ripple is directly added to the actual (sensor-)signal.
Sidenote:
To get a better grasp on the ripple, I made an AC-amplifier by using an opamp with amplification of 18k/1k noninverting (I had some free pins and soldered a series cap to in+ and two resistors for the amplification. The scopeshots below are all made with signals amplified by this helper-amplifier, taken directly from the output). Furthermore the Volts/div are wrong by a factor 10 in the pictures, I used 1/1 probe, but had 1/10 set on the scope. So 50mV is actually 5mV.
Lets get to the Scope shots:
First, TP9 (the output) has a very rippely output:

In contrast, when measuring my supply (same 18x Amplifier used) it looks quite ok:

The output of the most right opamp has really much noise (pin 14). Note the 200mV instead of 50mV scale:

Although the inputs (DAC_REF_X, REF_1.65V) look ok as well:

My layout looks like this:

How come this simple circuit produces so much ripple.
Note: I am looking at the ripple (the low frequency change of voltage), not the noise, which is ok.
(The noise is some kind of 200kHz Signal, probably from my buck converters. If you think I should investigate this, I will)
Update: Ok, in-between-result: the 100pF made the noise on the first opamp go away, so this is progress:) Secondly, something in my workplace seems to induce the 200kHz "noise" into my circuit (or rather the probe), and as I thoroughly twisted my supply cables, it got better. Third: I added 100pf on +15 and -15 to gnd, but the problem remains. However, after the excess noise on opamp one was gone due to the 100pF||18k, I saw the ripple (as shown in Pic 1) clearly on the output of opamp one (that would be picture 3 looking like pic 1 now). And lastly: I have three channels, and had the strange phenomenon that all three channels stopped having the ripple alltogether (although I made changes to only one channel). But it came back after a few power cycles.


texts: Alternative to cartridge heater for 10mm deep hole?

texts:
I am designing my own version of a heater block for a 3D printer hot end. I had originally intended to use a 40W cartridge heater but the shortest length available I can find is 20mm and the geometry of the block only allows for a 10mm deep hole.

The heater cartridge is to be used in conjunction with a thermistor using PID control to maintain a constant temperature (approx. 200°C). Both of these elements being encased in the same aluminium block.

Is there an alternative I could use to a heater cartridge which would fit these requirements? I am unsure if a resistor could withstand this?


texts:
So be I recently asked a question about using a PCB design for a fusebox (link here: PCB design for automotive fusebox?) but since recently come across two other fuse alternatives: PPTCs and automotive circuit breakers.

As the current fusebox design goes, our max ratings range from 3A to 30A. Would a design using either PPTC or automotive circuit breakers be feasible?

As I understand for PPTCs the operating temperature would be required (not sure of top of my head but I assume it's below 85°C. Can update when I get the results back). Automotive circuit breakers at the moment seems the better option thus far. Any suggestions?


texts: Charging lithium-ion cells in series individually with multiple CC regulators from a single power supply

texts:
I'm looking to build a battery pack from lithium-ion 18650 cells, 13s16p (parallel first) to achieve around a 50V (nominal) battery pack.  I realize there are probably charge solutions out there with the proper voltage and BMS which can be used to charge the entire pack with balancing and protection; however, my idea is to use a single adjustable buck CC power supply on each parallel cell pack to keep it charged to 4.2V while in series, and then power all of these supplies with a single larger amperage AC-DC 12V supply which can be powered with 120V AC.

I'm wondering if having all of the individual battery chargers powered by the same supply will be a conflict while the packs are wired in series (the inputs would all share a common ground).  Does each circuit need to be segregated with a transformer?  Is there another way to separate them?  Other pitfalls I'm not thinking of?


texts: Is there a TTL or CMOS shift register chip which has an output pin telling you when it has shifted out all (8) bits?

texts: Quick question, I'm going through 74x and CD4x chips to see if there is a parallel load serial out (left) shift register which would have the convenience of telling you when it is done shifting everything out? I am trying to avoid running an 3 bit counter on the side to know when all is shifted out.


texts: LDR not detecting light from LED when finger placed between the two

texts:
I'm currently working on a project which uses an LED and a photoresistor to work out my BPM.

I have a schematic which I've built into a prototype which all works fine and when I run the serial monitor in Arduino I'm getting output values.

The problem is, when I place a finger in between the LED and photoresistor, for some reason the readings are going to 0 and I'm unsure why?

I've encased with led and photoresistor to avoid any other light but for some reason I'm not getting any values.

Here is the schematic that i'm following:

You'll have to excuse my choice of encasement:

Unsure of what reasons which could be preventing the LDR of outputting.


texts: DALI schematic: help to analize reception circuit and limited current supply

texts:
I am trying to understand how this schematic works. It is a physical layer implementation of the DALI specification. The schematic is in this document
 (page 11). I have mainly two questions:

In reception mode: when the bus is idle (voltage level between 9.5 and 22.5 V, according to the specification) if the lower limit (9.5V)
is analyzed, the current through the optocoupler diode is: $$\frac{V_\text{bus (idle)}-V_\text{f (bridfe)}-V_\text{Z (D4)}-V_\text{f (U2)}}{R_6} = \frac{9.5-0.7- 5.1-1.25}{2.2\,\text K} = 1.1\text{ mA}$$
(approximately). With such current value, the U2 optocoupler transistor is not saturated and therefore, DALI_IN is not close to 0 V.
What am I analyzing erroneously? For \$V_\text{bus(idle)}=22.5\,\text V\$, the current is approximately 7 mA, so DALI_IN has a voltage close to 0 V
(the transistor is saturated).
Limited current source: The DALI specification limits the maximum current to 250 mA. In the schematic, the limited current source is
created with Q1, D3, R2 and R3 but I can not understand how it works. How are the maximum current value and the output voltage calculated?


texts:
An interesting fact I came across recently - electric kettles in the US run at double the time for other countries - due to the US adopting a 110V power system. (And electrical kettle boiling duration being proportional wattage available). (1500W in US and 3000W in other countries).

I'm wondering how this applies to charging batteries. Does it take longer or the same time to charge a battery (from the mains) in the US compared to other countries? (What are the factors involved?)

But that's wrong - it's related to amp-hours (for NmHi) to charge a battery.

In theory in the US you get 20 Amps from a wall socket. In Australia you get 10 amps.

That leaves me with a question - do batteries take twice as long to charge in Australia as the US? If I move from Australia to the US will my phone charge faster?

My question is: Is lithium battery charging speed proportional to the amps provided from the power source?


texts: ATmega2560 not responding on hand-assembled PCBs

texts:
I've assembled some PCBs that I had made, and I'm unable to get the ATmega2560 to respond to programming via the ICSP header. On the third board I'm trying, I have soldered on only the MCU, the ICSP header and a reset pull-up resistor.

Here are the things I've checked:

No shorted pins
Supply voltage to all the Vcc pins
Ground connection to all the GND pins
MOSI, MISO, SCK and RESET all have continuity from the header to the pins
The programmer works (tested with an Arduino Mega 2560)
That ATmega2560s are shipped with the fuse bits set to use the internal oscillator

The DSO shows RESET going low, clock, and MOSI coming in, but no MISO goes out.

What else could I check?


texts: PIC18 GPIO switch from input to output(dual mode)

texts: I have always wondered if it is possible to switch the port direction of the PIC GPIO during the course of the program execution. So, for instance I start with a particular port set as an input(digital level). I monitor that pin, and if the level changes, I change the direction of that pin and drive a signal to turn on a LED. Is this too far fetched or is it doable? If so, some pseudo-code to  would be very helpful.


texts:
I am searching for a functionally compatible replacement for the CM8870.

Would the HT9170 or MC145436 be suitable?


texts:
I'm trying to build a full bridge dc-dc converter and planning to apply a type 3 compensator(voltage mode). When I check the isolated feedback type 3, I've read some comments indicate that it's hard to apply in practice. Than I decided to do it in another way but I'm not sure if it's going to work or not.
I'm planning to put the pwm IC on secondary side so there will be no need for isolating the feedback, and feed the IC from input voltage through an isolated dc-dc module, and use a isolated gate driver, then I can apply non isolated type 3 compensation but still maintain the isolation on circuit.
Here is my circuit plan:

simulate this circuit – Schematic created using CircuitLab
Question is: Will it work?
(output voltage is 350V so the pwm IC will be on same ground with a 350V output)
Complete Circuit:
(component name and values are random)

simulate this circuit


texts:
I'm trying to calculate the peak reverse recovery current \$I_{RM(REC)}\$ of a diode from information given on a typical diode datasheet (really what I want is the transit time TT, but the only piece I'm missing is \$I_{RM(REC)}\$).

A few sample datasheets for the 1N4148:

MCC semi: \$I_F = 50mA\$, \$I_{rr} = 0.1 I_r\$, \$R_L = 100 \Omega\$
Fairchild: \$I_F = 10mA\$, \$I_{rr} = 1mA\$, \$R_L = 100 \Omega\$, \$V_R = 6V (600mA)\$
Diodes INC: \$I_F = I_R = 10mA\$, \$I_{rr} = 0.1 I_R\$, \$R_L = 100\Omega\$

Relevant equation:
\begin{equation}
Q_{rr} = I_F TT = \frac{1}{2} t_{rr} I_{RM(REC)}
\end{equation}
Or,
\begin{equation}
TT = \frac{t_{rr} I_{RM(REC)}}{2 I_F}
\end{equation}
Additionally, typically \$t_{rr}\$ is measured until the reverse current has dropped to \$I_{RM(REC)}/10\$ (JEDEC JESD282B01, though it seems sometimes perhaps  different ratio might be used?).

LTSPICE lists the 1N4148 as having TT=20ns, so this is the figure I am aiming for. All the datasheets list \$t_{rr} = 4ns\$. That means the ratio of \$I_{RM(REC)}/I_F\$ I am looking for is 10 (non soft reverse recovery diodes).

MCC semi

Because \$I_F = 50mA\$, somehow I need to find \$I_{RM(REC)} = 500mA\$. The only other \$I_R\$ is for large reverse voltages, and is on the order of nA/\$\mu A\$'s. I don't know what the relation between \$I_{rr}\$ and \$I_{RM(REC)}\$ is.

Fairchild

Because \$I_F = 10mA\$, somehow I need to find \$I_{RM(REC)} = 100mA\$. I don't know what the relation between \$I_{rr}\$ and \$I_{RM(REC)}\$ is.

Diodes INC

Because \$I_F = 10mA\$, somehow I need to find \$I_{RM(REC)} = 100mA\$. Again, I don't know what the relation between \$I_{rr}\$ and \$I_{RM(REC)}\$ is.

How do I find \$I_{RM(REC)}\$ for these three example datasheets? Or is there not enough information given? If there isn't enough information, is there any other way to get an estimate on TT (what I'm really interested in) from the info in the datasheets?


texts:
So I have a relatively simple circuit. I have a little float sensor that is connected to a 24V circuit and when that float sensor is triggered (water is too low in the container) it connects the circuit, which triggers a solid state relay to connect a 120VAC circuit to turn on a pump which pumps up the container until the float sensor disconnects. I would like to add a status LED on the side of the 24V, probably on the low side of the SSR, so that I know when it is pumping and when it is off. Is there any clever way to add a 5V LED onto this circuit, or do I just need to bite the bullet and buy a 24V LED? I've included my circuit below:

UPDATE:

Here is the updated schematic based on the help I've received:


texts:
I have a lead-acid battery on which I am using a voltage divider to measure the remaining charge.

Its my understanding that an example battery could discharge from 100-0% over say 10.5V - 12V.

What I would like to do now is try to increase the resolution of output of the circuit.  So that an input of 10.5V-12V would be linearly related to an output of 0-5V.  How can this be done?


texts:
I have the following Stereo Jack Socket, but I think Its pin layout is different than the socket images available on the internet.
Please show me how to connect this female socket to the circuit (L, R, G)


texts:
Most generally I'm looking to design a UPS for a low power DC device given higher voltage AC current, with storage handled by a supercapacitor, or a bank wired in parallel.

For my specific case I'm looking to power a RasPi driven from 24VAC 3 Amp HVAC transformer with backup from supercaps in the 2.5V - 3V range.

Some similar commercial products exist, the closest being Juice4Halt, and several LiPo (UPiS) products exist, and more general battery driven options have been questions on this site before. I'm only aware of one project using supercaps, but they're wired in series and between need for capacitor balancing and not using a boost converter the usable time on backup power is more limited than possible and inefficiencies can be reduced. I'm wondering what the most efficient topology for this system would be.

Currently the two methods I can think of each have relative values and I don't have the experience to pick the best, or to know if I'm not thinking of a better idea.

The first is the simple method seems to be (24VAC->Rect->2.4VDC->5VDC->Load):

simulate this circuit – Schematic created using CircuitLab

A more complex version would be buck to 5V then a bidirectional Boost/Buck to the caps (24VAC->Rect->5VDC(<->2.5V)->Load):

simulate this circuit

My expectation is that the second version would be more energy efficient assuming the power source was generally available, but that the first design would work better given a blackout or brownout situation.

Which one would be the most efficient considering both energy usage and power factor? Would either one be more likely to work as expected in most situations? Would either design cause power issues for the load device (RasPi) while the caps are initially charging? Anything else to watch out for/gotchas to know about?


texts: What to look for in an Inertial Measurement Unit?

texts: I'm trying to implement an inertial measurement unit (IMU) in a project of mine, but I don't have much experience in this field. There's some terminology that I don't understand. For example, what does In-Run Bias stability, Random Walk, and bias repeatability mean. I have googled these terms, but still don't have an understand of them. For my application, I need to measure linear acceleration, velocity, and position (I am aware of the drift issue) and roll pitch and yaw of a vehicle.


texts: Passive proximity detection using metal plate-capacity

texts:
For some specific product, we need to create a proximity sensor of 50-100cm using a capacity sensing .(no PIR, no infra,no ultrasonic)

Reading on the net, haven't provide me what i needed .

So, i am trying to get some direction on how do you calculate  the plate surface area and thickness, in relation to the maximum distance of detection of a human body .

The software probably much easier, although i will also need to find a way so that it can awake the controller only on detection .

Is there something like that, or is this a very wrong direction ?

thanks .


texts: Beaglebone Black - Power sensors after boot

texts:
I am new to electronics and want to build a small thermometer/humidity sensor powered by a beaglebone black to get started on something practical.

My issue is that the board doesn't start when the sensors are powered. My connections are equivalent to:

simulate this circuit – Schematic created using CircuitLab

The 5V is coming from a barrel jack and it receives power even when the BBB is shutdown. And this is bad, according to the manual: "DO NOT APPLY VOLTAGE TO ANY I/O PIN WHEN POWER IS NOT SUPPLIED TO THE BOARD". Which is true, if I power my sensors after the board is booted, everything works fine. Otherwise the board won't boot.

Is there a simple way to add a GPIO controlled switch on the 5V rail between the barrel jack and my sensor array ? Is a PNP transistor enough ? Do I have to use a relay ?

The previous answers I found here talked about a tri-state buffer, but I couldn't understand how it would relate to my problem. It seemed to only apply to logic gates; Can we source current from a tri-state buffer ? ('im really new to this). Or am i supposed to use 1 tri-state buffer for each of my inputs ? (instead of controlling the power line with it).

This is what I had in mind:

simulate this circuit

There would be no voltage applied to ANALOG_IN until SYS_RESET is driven high.

Thank you for the help!

Update:
New schematic

simulate this circuit

I guess I don't need a resistor between Q1 & Q2 as R1 will do the job. Is this correct ?


texts: I was wondering whether there is a difference between Zener effect and Avalanche effect? How do they differ?


texts: Advice... Shift registers, multiplexing, or both

texts:
I'm doing a project that has a lot of displays, in the form of single leds or 7-segment displays. So the question is in the title. Using 8 bit registers, if I used them for all the leds, it would take around 60 registers, which is not a money problem given that they are like 20 cents each, but I don't know if it's absurd to do it.

The other option is to multiplex, specially with the 7 segment displays. There are like 55 of those displays, but I'm going to use an Arduino board and I doubt the processing speed will be enough to multiplex them all without blinking.

The other logical option is to use a combination of both, which I wouldn't know how to combine properly, maybe have little groups of up to 6 multiplexed displays, using the registers to control them all.

By the way, I have deduced that with pulse of around 10 microseconds of the clock for the registers, and 8 bit each register, it gives around 80 microsecond per register: 4800 microsecond totally, so about 5 milliseconds to work all of them. I don't know if this will be enough for a proper display of them all, although I could cut back the pulse to 2 or 4 microsecond and see if the registers still work properly.

So that's it, I'm asking for advicen before starting to design the circuit boards and buying registers, if anybody has experience on this things, I would appreciate it.

The board is also supposed to run more things than the displays, a bunch of servo motors, some steppers, and some inputs too (like another 60 inputs), so that will obviously affect time too. I could use a max of two microcontrollers if needed. If I could do it with one, perfect, if not, two at most. I could also change to Arduino DUE, which has a better processor, if that makes any difference.

Thanks in advance.


texts: Why is my 50-600V voltage tester able to detect 3V?

texts: I used non-contact voltage tester to test burned out Christmas lights. It says it can only detect in the range of 50-600V. One of the strings has 40 bulbs in series and none of the lights are burned out, so plugging it into a 120V outlet means there should be a 3V drop across each bulb, so my 50-600V tester shouldn't be able to detect that, but it does pick it up. Does anyone know why this would be?


texts: Powering LEDs with a computer's power supply

texts:
I have 10 of these boards OctoBright CYANEA v2.0 connected in series, controlled by an Arduino.

Powering one or two off of the Arduino 5v pin has worked for testing. Now I want to scale it up to 10x boards. I been told that a computer power supply should be able to handle the load from all 10 of these boards in series.

Each board at max brightness consumes 500mA. 10 * 500mA = 5 Amps max

My questions are;

Do I need to add any power conditioning to the output of the computers power supply?
Can I directly connect the 5v rails from the computer's power supply to these boards?
Anything I should know before I wire this up?
Can I power the Arduino from the same 5v rail of the computers power supply?


texts:
I have an old fridge evaporator fan motor and cannot figure out what "in" in the specifications mean.
I ordered a replacment motor and it does not have "in" in the specifications and after installation the fridge does not provide cool air in the fridge compartment. All the other specifications are the same.


texts:
I have taken up a "follow me" robot as my course project ,i am taking the following approach:

Use one SR04 ultrasonic transducer only as transmitter which will be with me.
Another SR04 module only  as receiver which will be mounted on the robot.

I just know how to calculate distance using one transducer (SR04) ,but in this work I need to use only one as a transmitter and the other only as receiver.Is there any way where we could achieve above mentioned.

All I need is my robot should follow unique person and tracking distance less than One meter.
If there is any other method welcome ..


texts: What are my prototyping options when working with smt devices?

texts:
I have been working on a project which will allow me to learn how to charge Li-ion batteries.

I recently purchased some simple PMIC's made by Texas Instruments. I received them the other day and realized I made a mistake in my purchase, the PMIC's were sot-23 smt packages.

I don't have much soldering experience, and most of my experience with electronics is with through-hole bread-boarding and through hole soldering. I hear a lot that smt is the way to go if your serious about electronics, so I don't know if I should consider returning them and sticking to what I know, or taking the leap into smt now.

Here are some things that I have to consider:

I already have a breadboard power supply, which I intended to use during the prototyping phase for charging. I don't know enough about SMT to know if I can still use it in such applications.
I can return the smt PMIC's, but the through-hole PMIC options I have found so far cost three times as much as the smt alternatives. And after reviewing some datasheets, I have found them to be way more complicated than whats actually necessary for my needs, I would be going from 6 pins to 16, with a bunch of added features I didn't need to deal with just to learn how to charge my first lithium battery.
I have reviewed the datasheet for the smt's I purchased about three times now, and it requires less than a half-dozen supportive components, most I had already or have purchased, such as NTC resistors.

Based on all that, I would at least like to know what are my prototyping options when dealing with smt devices, so that way I can make an intelligent decision on whether keeping them is even practical at this moment.

I'm assuming the four breadboards I have laying around are useless, so what can I use to setup and test circuits with smt components?


texts: Analyzing reflection and transmission without a VNA

texts:
The wikipedia page for network analyzers mentions "reflection and transmission of electrical networks are easy to measure at high frequencies" but doesn't give any hint on how this is done or what it is that's called "high frequencies" there (I'm guessing it's the GHz spectrum...)

Does this means I can do without a VNA in such cases (using just, say, a spectrum analyzer?)

Could someone elaborate?


texts: Why might a condenser microphone suddenly only record very close sounds?

texts:
I have a condenser microphone which is powered over USB (MPM-1000u if you care - it has a cardiod pattern).
It was working fine, but recently it seemed to stop working - it didn't seem to record anything.  However, I discovered that if I have it directly up against my lips and speak, it seems to record just fine.
Perhaps it's been too long since I did E&M, but I can't think of any reason that this would have happened.  I can imagine sound not being recorded well, or at all, but this eludes me.
Can anyone explain to me what could have happened?


texts: 4026 + 7-segment display: do I need transistors?

texts:
I'm a beginner and, as an exercise, I'm building a digital clock using without a microcontroller. The main IC that I'm using is a 4026, which counts and converts do 7-segment led format.
The leds in the 7-segment glow very dimly. I'm reading the 4026 datasheet, and trying to make sense of it. The diagram (reproduced below) seem to imply - if I'm reading correctly - that I would need a transistor for each one of the leds in de 7-segment display. My display is common-cathode.

Since I'm building a digital clock, this would mean that I'd need 6*7=42 transistors, which seem like overkill for such a simple project. I also saw some similar projects on the internet that don't use the transistors.
Should I put all the transistors in the circuit? If not, then how can I make the LED glow more brightly?


texts: MODBUS RTU reading on Jetson Nano over RS485

texts:
I'm trying to implement Modbus reading on Jetson Nano (Linux - Ubuntu operation system).System include 3 part:
-MODBUS device which I would like to achieve input registers. --> Krohne Signal Converter-IFC050
-USB converter --> RS485 to USB(UART) reading. I can see the CH340 driver on Jetson Nano.
-Jetson Nano --> NVIDIA's development board. I'm using SSH connection to connect Jetson Nano.
I'm using pyModbus library on python which like:
from pymodbus.client.sync import ModbusSerialClient

client =  ModbusSerialClient (

method = 'rtu' ,
port   = 'dev/ttyUSB0',
baudrate = 9600 ,
timeout = 3 ,
parity = 'N',
stopbits = 1 ,
bytesize = 8   )

for address in range()

if client.connect():

   res = client.read_input_registers(address = 30000  , count = 20 , unit = 1 )

   if not res.isError():
       print(res.Registers)
   else:
       print(res)

else:
     print('Can not connect to the Modbus Slave/Server')

I'm sure about configuration which is 9600 baudrate , 8 byte , 1 stopbit , etc...
When I try to run the program it always return false which says 'Can not connect to the Modbus Slave/Server'.
What could be the problem about this matter? I can see CH340 driver(USB converter driver) on Jetson Nano as ttyUSB0.


texts: I am curious what methods are most suitable for securing PCBs. I have a large PCB which is fixed to a sheet metal enclosure using #4-40 x 1/4" stainless steel screws. The receiving end is a #4-40 captive standoff (PEM product). Initially I was not doing anything to prevent the screws from vibrating out. Sure enough, I started getting complaints that the screws were backing out just during shipping alone. So, I started to use a loc-tite product. This works well, but it's very labor intensive to put a drop on each screw. I have not used a lock washer as it tears up the PCB. Any suggestions?


texts: Reverse recovery time of Schottky diodes

texts:
I am considering redesigning a IR2110-based H-bridge driver with 1N5819 because UF4007 he called for is, strangely, not available from local suppliers. I understand that the author chose it for its fast speed, but I am wondering whether Schottky diodes are faster.

I have no intention running this circuit anywhere over 20V. It draws power from a car battery, or perhaps a running car.

Here is the circuit I am modifying:

The same speed issue exists in the body diode of IRF540 power MOSFET I chose to use. Transformers have flyback issues and the same switching frequency is also applied to the switching MOSFETs' body diodes as well. Will a MBR1045 power Schottky diode help?

Not quite in topic, if I replace the bootstrap cap C1 with a MLCC (47uF ceramic caps in 1206 and 0603 sizes are available from local suppliers, despite being quite expensive) can I get away without C2?


texts: LUT from OTP vs LUT from register on e-paper displays

texts: What is the meaning of LUT from OTP and LUT from register on e-paper display convention?How could we program the e-paper display using LUT from register? I'm working on GDEW0213T5D e-paper which uses UC8151D driver and I'm trying to program it.When I'm using LUT from OTP, screen runs 3 different state; completely white , completely black and almost completely(there is a white window the outer side) black screen. I can not program the e-paper to working properly. When I'm using LUT from register algorithm, e-paper screen maintains the last situation e.g. there as no any action on the screen.How can I activate the e-paper?


texts:
I'm building a multi purpose battery box for the car. It'll have at least a USB and a 12v cigarette lighter output, and retractable clamps for connecting straight to the car battery in the event that the car won't start, which has been happening lately. It'll charge from the car's cigarette lighter when the car is running.

My question is, what would the recommendation be. I'm using 18650 lithium cells, since I want at least a 12v output, should I put 3 or 4 of them in series with several series sets in parallel, or should I put them all in parallel and step up the voltage to whatever is needed? 4 fully charged cells in series would be 16.8 volts, too high for the car battery, but approaching dead it would be around 12v. If I step up the voltage I can control the output precisely, and I know the cells can handle the current output. Any advice?


texts: Why are some AVRs marked with 'atmega' and some marked with 'mega'?

texts: I'm working on hacking the MCU in my MLP4DSM radio for an RC helicopter. The model number on the MCU is scratched out, but I can clearly read MEGA without an AT at the beginning. Google is letting me down. However, I can find AVRs marked either way scrolling through Google images. Whats the difference?


texts: Determine the power dissipated in W in the 5 Ω resistor

texts:
simulate this circuit – Schematic created using CircuitLab

Excuse me for my really bad use of the schematic feature I just didn't know how to switch to the phasor domain. Anyway, I'm asked to find the Power at the R2 Resistor knowing only that the capacitor absorbs -2.3 VARs of reactive power.

I've been stuck on this problem and just couldn't find a way to solve it so I just need something to focus at or maybe get some power properties I should know.

(And yes, we don't know how many volts the source is generating)


texts: Difference between 2.4Ghz ISM and IEEE 802.11 frequency bands?

texts:
It may be a silly question to ask the difference between a frequency band and a standard protocol which is represented by IEEE.
But, I've been reading the wikipedia page of the IEEE 802.11 and it says that the frequncy band is 2.4Ghz ISM and i was massively confused on this problem.

  What's the difference between 802.11 and 2.4Ghz and why they can't be used to be connected together(like connecting an nRF24L01 to a Wireless LAN?

The wikipedia page of 802.11 says that it uses the 2.4Ghz ISM band. So there should be no problem connecting an nRF to a Wireless LAN.

Thanks in advance.


texts: How can I estimate the readout time of an electronic camera shutter?

texts:
I would like your help in finding a way to estimate the readout time of a digital camera's rolling (electronic) shutter. Meaning, the time that it takes to scan a frame. I looked through the internet for ways to estimate it, but I couldn't find something.

I would highly appreciate any given help!


texts: Raspberry Pi CM4 I/O board 2-layer PCB design

texts:
I am a beginner in PCB designing, well in past experience, designed an PCB with some sort of digital signals, power (AC/DC) lines and USB.
Now I am working to design the PCB for CM4 I/O board with GPIOs, CSI, HDMI, USB-OTG, USB type-C, SD card connectors.
I am posting schematic and PCB layout here. Please suggest your inputs and issues in this, that can save me on cost and time. I am happy to incorporate that.
Schematic for GPIO connector

Schematic for high-speed signal connector

Overall PCB

USB signal routing

CSI signal routing

HDMI signal routing

Power and GPIO signal routing

As in a single image it is quite complicated to see, so I put the snapshot of different portion. Let me know if you need any other detail or info, I am ready to share.
PS: I have not filled the ground plane, so that the layout is clearly visible.


texts: I have SN74HC4040 12 bit counter, however, I need only 10 bits and then reset it back to 0. Would it be reliable to use 11th bit as an input to the CLR (reset pin)? Basically, when the counter transitions from 1023 to 1024, the 11th bit becomes high, which, in turn, sets CLR to high and resets the counter. It seems to work, but I do not know how to check the counter's state during the reset period.


texts: How to calculate total power from spectrum?

texts:
I'm trying to measure total power(dBm) from the following spectrum, the spectrum is 5MHz wide, the peak power from the spectrum is about -40 dBm,

I have an array of spectrum points(Power vs Frequency), now my question is how do I calculate total power from the array?

I assume that first thing to do is to convert array values --> log. scale(dBm) to linear(mW) and I got stuck here?

any suggestions would be much appreciated.


texts: RC Network resistor power rating with DC supply

texts:
If this was wired up, what is the power rating the resistor needs to be? Initially there is 17.5 Watts dissipated by the resistor, but this is for a very short amount of time. So, for instance, would a 10W resistor suffice?

Does the power rating need to be different if the supply is pulsed on/off compared to being on steady? Does the capacitor size matter in choosing the correct power rating of resistor?


texts:
I'm reverse engineering a laser printer (Laserjet 1320) and I need to infer some things about the memory bus. The full schematic I've made while reversing is here (in pdf) on Drive. I'm not all that familiar with embedded hardware memory mapping and this part confuses me:

The processor is a Freescale ColdFire-based device (in particular, with a ColdFire v2 core) but the particulars are proprietary. Regardless, ColdFire is basically M68k so I would assume the processor address bus is either 24 bits or full 32-bit. The program is stored in mask ROM U8, connected to the 14-bit address bus (A0:A13). Then, address bits A14:A20 are connected to D-latch U5, loaded loaded by A4:A10.
Here's the datasheet for the mask ROM, and the datasheet for the D latch. When U8 is disabled (nCE HIGH) the latch is transparent; then U8 is enabled (nCE LOW) and the latch latches. What I'm wondering is, how is this implemented on the processor side? First, a bit must be set HIGH, then bits A4:A10 are set, then the pin is set LOW, and pins A0:A13 are set. But how does the processor actually access these addresses when they're provided? Does it require two clock cycles when changing the significant bits, and if so, is this a processor issue or an external hardware issue?


texts: Self-inductance of toroid of rectangular cross section (N=windings?)

texts: I have found a lot of answers about how to calculate the self-inductance of toroid of rectangular cross section, however my question says that "The winding are seen as a thin homogenuous currentlayer around the core" (excuse the translation). What does that mean for N? Does it mean N=1?


texts: LabView drivers for Keithley 6487. where to find documentation?

texts:
I have to set up a program for measuring the IV characteristics of some components using LabView.

At the time of writing I'm studying the basics of the G language (LabView programming language) for loops, while loops, etc... I'm not new to programming.

As far as my understanding goes, an IV curve can be obtained by sweeping the voltage across a predefined range and then measuring current. This can be done by using a for loop, for instance.

Bear in mind that I come from "conventional software programming" and I'm used to have full readable and complete documentation. Furthermore, I have little experience with lab equipment.
My problem is that there seems to be a lack of documentation of drivers and I don't feel comfortable with this going on with the project.

Take the Keithley 6487 for instance. Both a DC voltage source and a picoammeter. The page of the drivers is here and I see no sign of specific block documentation. There is just some reference to how block should behave generally depending on the category they belong to (such as Initialize, Configure, Data, ecc...). This looks a bit concerning to me, but bearing in mind that at the moment don't have the instrument here, and I don't know it, it might very well be that matching each block to a specific function of the instrument is very easy and just requires a knowledge of how the instrument works. This would explain the lack of documentation, at least.

Could someone tell me where to get specific documentation for instrument drivers for LabView? Kethley/Tektronix does not seem to provide it...


texts: Will giving 9/12v to a quolcomm quickcharge device kill it?

texts:
Background

I recently broke my phone's USB port (damn!), so as a stopgap measure before I can be bothered to buy and fit a replacement, I've soldered two wires to the +ve and -ve wires of where the port used to be  and I've fitted a barrel jack on the outside to act as a makeshift charging port. I've got a problem, however, that it only draws ~500mA. This is very slow for charging. I believe that this is due to it trying to conform with the USB 2.0 standerd (i.e. no more than 500mA).

Actual question

My phone has Qualcomm quickcharge. Can I feed 9 or 12 volts directly to the USB power pins, or is it neccessary to perform some kind of handshake first? (i.e. do I have to take it all apart again and solder on USB data wires?) Or, is there any other way I can increase the charging speed?

Thanls in advance.


texts: Orcad/PSpice - How to add V0, V1 for PSpice

texts: I have my Circuit and PSpice solves it correctly. However, I want to measure the voltage across a specific place, V0. How do I add the marker V0 into my circuit and have PSpice solve for it?


texts: Wouldn't putting an electronic key inside a small Faraday cage render it completely useless?

texts:
Am I missing something? The Engadget article Kia made a tiny Faraday cage to protect your wireless key from thieves says:

  Many existing keyless entry systems aren't secure, but few people are likely to replace their cars just to reduce the chances of a determined thief making off with their ride. Kia UK has an official stopgap solution, though. It's taking a cue from third parties and releasing KiaSafe, a case that serves as a minuscule Faraday cage to block the key's wireless signals. There's nothing particularly special to it -- it's ultimately a metal-lined pouch -- but that's all might you need to prevent someone from swiping your car while you're asleep.

I'm confused in more than one way.

I'd thought that the point of a Faraday cage for RF signals is to block RF inside from getting out and RF outside from getting in. So then you'd have to take it out of the Faraday cage to use it and then of course the usual intercept mechanisms can still take place.
If your radiating source is positioned flat up against or even a fraction of a wavelength away from (at least a wire mesh) Faraday cage, don't you then get significant leakage anyway?


texts:
I'd like to make sure the voltage along a DC system of a building keeps stable.
Consider I have the main power station with solar input current and main batteries.

Can I put batteries in parallel along the circuit where more load is expected?
Do they align to the same voltage even though they are far away from each other?

I'd like to do such thing to lower dissipation on main cables and also to put AC only where needed.

I'm asking this because placing an inverter far away from the batteries caused it to lose power. So I thought I could place a backup battery in parallel right before it.

What are common practices about this problem?


texts:
I recently bought this 8x8 LED board from geeetech which came with this datasheet. I'm new to programming so I bought this board to "figure it out" but now I'm running into issues I don't understand.

For starters, I've noticed that I can only get one color value out of an individual LED. By hooking up pins 9 & 1 I assumed I would get a magenta looking color but I only get solid red. If I unplug pin 9 then I get solid blue. What am I missing here?

Lastly, I accidentally already blew two of the RGB LEDs by hooking up straight to a 6v source. So now I'm using a potentiometer to control resistance (rather than a resistor), is this okay?


texts: Is it safe to use PC analog output card as current source?

texts:
I have a very PCI analog output card which could output a voltage ranged from 0 to 5V. I need a circuit to output a current ranged from 10mA to 90mA. The load is about 45 Ohm.

So is it safe to connect directly the analog output to the load and change the voltage until we get the desire current? Will it burn the card if it is not correctly connected?

I am sorry that I don't have much experience in circuit building. But I read other article about using op-amp to control the output current by input voltage.

simulate this circuit – Schematic created using CircuitLab

I wonder if the above schematic is a correct setup to apply a current to a load? What's the advantage to the op amp for this purpose?


texts:
I am going to start off with the disclaimer that I have a Software Engineering background and very little electrical engineering background.

I am using a 3q triac on a breadboard circuit. My gate current/voltage is supplied by a a 9VDC battery. The circuit I am using is more or less represented here:

When I use a 3q triac, my load is getting about 5/6th of the voltage. The rest is dissipating across the triac. The waveform is chopped off/flatted above a certain voltage and becomes sinosidal again below it.

When I use a 4q triac, I don't face this issue.

The 3q triac I have been using in the circuit is T405-800B-TR whereas the 4q triac I tried is BT138-800,127.

Is this normal for 3q triacs to eat up some of the Voltage or is there something wrong with this particular triac that I am using?


texts: Setting minimum output voltage of boost converter with potentiometer and resistor

texts:
I am designing an LED light project using this Cree XLamp LED, (Forward voltage is 36V, forward current is 2400mA) and I am looking for a way to limit the output voltage of a boost converter by adding a potentiometer and a resistor. For reference, this was demonstrated in this video. However what I don't quite understand is how he chose to select a 6.8k ohm resistor to run in series with the added potentiometer.
What I believe is confusing me is the basic usage of Ohm's law. By my understanding, when the potentiometer is fully at the left and there is no resistance (through the pot), the total resistance is 6.8k. The output voltage of the boost converter is 6V. When fully at the right, the resistance is 9k ohms, and the output voltage is 12V. How can this be? What should go through my mind when trying to pick the resistor to use, since I'm wanting to use a different LED? Essentially, what is happening that lets the resistor determine the minimum voltage of the boost converter?
I know there's too many questions in my mind to ask them all, so I'll stick with the root of my confusion. Hopefully someone can understand my madness!
Thanks.