texts:
In my textbook we are given the question below. I understand how to get the answer of B. But I am confused as to why the answer of A is 10 volts where the difference is 20 volts.. 10 and -10? Where is my logic or understanding wrong?

In your circuit, two wires connected to a 10-V voltage supply happen to be very close to each other at a certain location; they are separated by 2 mm.

A. What is the voltage between the wires at this location?

  Wouldn't the difference be 20 V? But the answer key says 10 V, why is
  this?

B. What is approximately the electric field strength at this
location?

  (Answer A) / .002 = ..


texts: Building BLDC ESC - question on PWM duty-cycle vs motor speed

texts:
I'm currently working on a simple ESC design to drive a small BLDC motor (6A continuous max). I'm at a stage where I can start the motor reliably, but haven't yet achieved closed-loop control using zero-crossing. I have done some experiments where I keep increasing the commutation frequency, but at some point the motor stalls. The PWM duty cycle doesn't change as I increase commutation frequency.

My question is, does BLDC motors require higher current (increase in PWM duty cycle) at higher rotation rates? This is my intuition as higher current results in stronger magnetic field, which results in "faster" rate of change in angular velocity.

I want to spin the motor at higher frequencies reliably, that's all.

To clarify some of the terms,

Commutation Frequency - how fast the commutation steps change (1->6). This leads to changing speed in BLDC motors

PWM frequency - PWM signals are given during each commutation. Varying duty cycle here simulates varying supplied voltage to motor (and hence current)


texts: Can I run a fan from two power sources with differing voltage simultaneously?

texts:
EDIT For clarity please see the answer from Richard Crowley.  Essentially I want to achieve his circuit with an automatic switch via a pre-set max temp.  Really appreciate all the help so far.  Thankyou all  ******

So I want to vent my home server room as it is getting toasty.  I have been running a couple of fans rigged into a homemade vent system to allow airflow. I use a voltage regulator to control fan speed and they have been fine but now cant handle the midday heat- fine rest of time.

What I want to do is keep them wired as they are but add in another power loop with a higher voltage wired through a temp activated switch. Unless I've messed my logic this should allow current cooling for most of the time but when it gets toasty the switch should trip and the fans will get a power boost= more CFM= more cooling till temp drops then back to normal again.

Will this work?
thanks


texts: Is the potential in "potential difference" the short form of potential electric energy?

texts:
Just a few days ago, we were taught the basics of electricity in the IGCSE Physics syllabus. While he's said a great deal about potential difference and how it's the difference in voltage between two points in a circuit, he never bothered describing what "potential" itself was.

From what I have learned both from our physics teacher and the Internet, I guess it is actually just the short form of "potential electrical energy".

If it is so, why is the term so less discussed?


texts: Working on a project, where we need to measure the change in capacitance(capacitance change roughly from 0.5 pF at the start, to 20 pF at the end of the measurement). On the variable cap, only the distance between the plates of the capacitor is changing. I was thinking about RF oscillator, but have no idea, how to convert the frequency to voltage. And if this is even suited for such an application and it must have at least 10 measurements per second. I'm a newbie in this field so it would be great if someone could explain to me the circuit diagram for this application.


texts: Cannot change DMA configuration after first transfer

texts:
I'm using a stm32f10x microcontroller and I'm trying to program its DMA module for normal mode transfers.

The first transfer works perfectly, but after it's over, I try to change the source, destination, size, or any other of the other configuration parameters, one of two things happen:

Either the flag remains high the entire time and no other transfers occur;
Or (happens when I clear the flag), it doesn't matter how many times I write the DMA_Cmd(DMA_Channel1, ENABLE), it doesn't do anything, even though the transfer complete flag is reset;

Any ideas what could be wrong?

PS: I'm using the device's library


texts: I am trying to use the octal bus transceiver SN74LS245N and it is not working. I have power going into pin 20 using 4 1.5v AA batteries, Ground on pin 10, output enable low on pin 19, the direction pin high on pin 1, A1 on high pin 2, and B1 on the voltage side of a red LED. As far as I can tell it is supposed to (when output enable is low) send A1 to B1... This is not the result I am receiving. When I put A1 high it turns on the LED, when it's low it turns it off. Here's the weird part, when I turn off pin A1, B1 stays on for a moment, if I only unplug the input side of the wire it turns on the led, and when I have the cord completely unplugged it will sometimes randomly send power to the LED. Am I doing something wrong? If so, how can I fix this?


texts: pH sensor, is the cebo-lc device suitable?

texts:
I would like to interface a pH probe. I know there are various threads on this topic. If found this two most interesting:

Miceuz suggests two suitable instrumentation amplifiers (INA 116 and AD549). In this post markrages suggests in one of his comments to just use single ended amplification if there is not a lot of noise due to common mode voltage. However, he also stresses that simple instrumentation amplifiers would not work here.

The cebo-lc has an AD8692 with an input bias current between 1 and 50 pA. That is far more than for e.g INA116 (10 fA). Is the CEBO-LC therefore unsuited for this task ?


texts: Why does VHDL not allow to alias slice of an array in this way?

texts:
This code does not compile:

  type array_1_t is array (0 to 73) of std_logic_vector(31 downto 0);
  type array_2_t is array (0 to 22) of std_logic_vector(31 downto 0);

  signal my_array_1: array_1_t;
  alias  my_array_2_1: array_2_t is my_array_1(0 to 22);
  alias  my_array_2_2: array_2_t is my_array_1(23 to 45);
  alias  my_array_2_3: array_2_t is my_array_1(46 to 73);

The error is "The type of aliased object does not match the type in the alias declaration."

Both of these arrays are of std_logic_vector(31 downto 0). When then does this code not compile?


texts:
I am trying to interface a pair of Chinese calipers with my Arduino. Due to the calipers running at 1.5v, I've used a TPQ-2222 (quad 2N2222 transistors I think, please let me know if I'm mistaken) to step up the voltage to 5v. However, on power up, the Arduino fires voltage down it's pins randomly and I'm worried that that voltage may damage my calipers. Unfortunately I don't have any diodes on hand (they are on order from china, ETA 2 weeks...but they were cheap! And I'm not paying $3 for 10 diodes at my local electronics shop!)

Can I use the transistors on the TPQ-2222 as a signal diode and is it necessary because the transistor amplifying the voltage will already work as one?


texts: How to model output pin of microcontroller in SPICE?

texts:
I'd like to model an output pin of a microcontroller (MSP430F5xxx) in SPICE.  The datasheet contains this:

This is the I-V graph for a pin which is configured as output and set to logic low.  There is an equivalent graph for a pin set to logic high, which is almost exactly the same shape but reversed (negative large current at V=0, zero current at V=3).

Is there a good way to reproduce this in SPICE?

Bonus question: How can this be made to produce either the logic low or logic high I-V based on an input voltage corresponding to the logic level?


texts:
I have a stepper motor and I've noticed that when I turn the spindle with the motor lead wires touching each other, that the motor strongly resists my efforts to turn it. When the wires are not touching each other the motor turns more freely. I have inferred from this that the current that is induced from my attempts to turn it is so strong that once it is feed back into the motor, it resists the turning motion.

Now that I have connected the motor to a driver, it is my expectation that turning the spindle would not cause damaging current to be feedback into the driver to destroy it. I am concerned that turning the spindle would damage the driver because the driver's documentation states that disconnecting the motor while the system is on will damage the driver IC.

My question is: Can turning the spindle while connected to the driver cause damage to the driver?


texts:
In literature zero sequence current is called DC component. If it was DC component then how a zero sequence current in neutral grounded secondary of a transformer cause current in neutral grounded primary?
Also why in zero sequence circuit (figure below) primary and secondary leakage inductance is not connected with reference bus?


texts: Controlling power to two RPis from Arduino mini pins, super low power - MOSFET?

texts:
I have a Arduino pro mini that, depending on circumstances, needs to switch power on and off to two Raspberry Pi Zero W's (don't worry I have a shutdown script running before power goes off). The switches need to be independent from each other as there will be the option of having neither RPi on. After much research and googling and youtube clips I have just about grasped MOSFETs, pretty much anyway, and this looks to be the best solution by far! So as I understand it, if I do the following for each RPi, it should work as desired, right? (Please excuse my not-very-technical diagram!)

Then I just set the pin coming from the pro mini to the gate of the MOSFET to high or low to provide power or cut power to the pi? Have I got that right? Thanks for all your help. I'm looking at this one specifically... CPC product link

EDIT --------------------------------------------------------------------------

OK, so after Elliot's comment I realise my mistake and I'm now looking at pMOS transistors. Looking at the diagram below, this looks to me like it should work:

So if I hook up my system as follows (only one Pi shown for simplicity)...

...then it would work as follows:

G goes LOW, RPi has power and boots.
Yellow wire goes LOW to trigger shutdown script in RPi, waits 20 seconds for shutdown to complete.
RPi, listening to pin 12, shuts down.
G goes HIGH, power to RPi is halted.

Repeat!

Is there a reason this wouldn't work? All connections to the RPi from the Arduino, bar the connection to the pMOS gate (just the yellow wire) are LOW when the RPi loses power.

EDIT --------------------------------------------------------------------------

Ok so it would appear I can't get a pMOS TH with the correct V and current values for my project, so looking at the RT9742ANGJ5F USB switch chip as an alternative solution, as suggested by Chris, this is my new proposed solution. Assuming I can nail the SM soldering, does this look like it will work?


texts: What are the 15 wires on my 700W BLDC servo motor for?

texts:
So I have this 48V 700W DC servo motor and I cannot find the datasheet from the supplier. Unlike most stepper and servo motors, this one has 15 wires coming out of it. It says that it has an encoder built-in, so I suppose that is partly why it has so many wires.

At least it has a sticker on it that gives some labels. Here is what the label says:

Red: +5V
Blue: A
Green: B
Yellow: Z
Brown: U
Gray: V
White: W
Black: 0V
Blue/Black: A-
Green/Black: B-
Yellow/Black: Z-
Brown/Black: U-
Gray/Black: V-
White/Black: W-
Shell: Shield

If you have any idea what this means or know where I can find out, I would really appreciate it.


texts:
I will preface this question with a caveat: I'm a reasonably talented programmer, but an absolute novice in electronics. This will be my first project.
My dad has a 1/19th scale model railway. I'd quite like to add announcements to the passenger trains, of the form "This station is X. Welcome aboard the HH:MM service to Y."
I thought it might be possiblw to swipe a "destination" tag at the beginning of the journey to set Y. X would be set by a tag at the station when the train passes/rests for a couple of seconds. The range, i guess, would be about 80mm from the building to the far edge of the track. It'd be worth bearing in mind that, being on a train, exact positioning will be a challenge and so either it'd need to be read just as the train passed the station or have a longer range to allow for stopping in the wrong place.
Does that sound (a) feasible, (b) the best way to do it, and (c) relatively easy?
Ideally the components would be fairly low cost. Adding some level of electrical power to the station buildings would be possible (they'd basically be balsa wood boxes).
Longer term, I'd be thinking about possibly adding other things on to this system (e.g. automatic points switching), but wanted to bring it down to a minimal system/infrastructure before attempting anything fancy.


texts: How do we extract the etchant after it is stopped at the boron layer in MEMs fabrication process?

texts:
Dopant-Selective etch stop method is where we create a layer of highly doped boron in the substrate to stop the etching process at that exact layer, but when that cavity is created the etchants are still in there.

Question: How do we remove that etchant?


texts: Designing a simple fan + resistor system for heating air

texts:
I have a research application that requires a steady supply of heated air. My current plan is to 3D-print a small tank (6" x 6" x 4") to which a muffin fan will be fastened. The fan will blow air across a 20W resistor into the tank to heat the air. The heated air will continuously leave the tank through an exit port and travel to the application for which the air is needed. The exiting air will need to be maintained at 37C +/- 1C.

Here is a schematic of the device:

To get the correct temperature, I will adjust the fan speed (variable CFM). This is my attempt at calculating the necessary fan speed:

Ambient air temp: T1 = 25C

Final air temp: T2 = 37C

Resistor power: P = 20 W

Heat capacity of air: c = 1 J/gK

Density of air: d = 1.15 g/L

air flow rate: f = P/[(c)(d)(T2-T1)] = 20/[(1)(1.15)(37-25)]

= 1.45 L/s = 3.1 CFM

This is not my area of expertise so I was wondering if I could get some feedback on my proposed method. Do the calculations seem sound? Do you foresee any issues with this system as a whole?


texts: Is there an opensource linting tool for Verilog. I've seen HDL companion and other but they all come with a price tag.


texts: I've recently purchased the MPU9150 IMU from InvenSense. Testing it, I'm astonished to see that, at rest, it constantly output 0.25 °⋅s-1 around the Z axis, -0.5 °⋅s-1 around the Y axis and -1 °⋅s-1 around the X axis. Is there a way to correct this ? Is this really normal ? I know there is a drift coming from gyroscopes, but with such values this will lead to enormous error in a few minutes...


texts:
I have two PCBs that I would like to connect/sandwich together via a 1x5 header on the bottom board and a 1x5 socket on the top board.
The components I have so far seem to work nicely, the only issue is the spacing between the boards. Due to some larger components on the bottom board, I need the spacing of the boards to be greater than 20mm.
I've seen a few board-to-board connectors out there, but they require you to solder both ends to each board, not ideal in my case since the boards need to be removable from one another.
What I need is some sort of "stackable spacer" header/socket combo, something that I can put between the header on the bottom board and socket on the top board.
Does anyone know if there is a product like this? I have thought of just using another socket like the one mounted on the top board, but after referencing the datasheet, the socket pins are too small to fit into the socket receptacles (by 0.1mm!)


texts: Reading an LED data sheet, voltage drop and supply voltage in an LED ring

texts:
I am looking to make an LED ring using these white LEDS.
I've drawn this schematic:

I was planning to use 5V supply so I followed Ohm's law and did 5/0.060 to get 83.3 so I rounded it up and used a 100 ohm resistor.
When looking at the data sheet there are 2 values:

Forward voltage
Reverse voltage

The forward voltage is 3.4V max, and reverse is 5V.
My understanding is that the LED with a resistor in series will act as a voltage divider, and the LED then can be operated from 5V.

Why is the forward voltage 3.4V?
I correct in assuming that 5V will be okay for this application with 100 ohms resistor?


texts: How can I use NAND gates to divide (5bit) binary inputs by an integer (say 5)?

texts:
Trying to sketch up a circuit which will divide, say a 5-bit binary number by 5 to produce a 4-bit binary quotient.
We can assume that the input doesn't actually reach 31, instead it's limited to 30, or 25.

I'd like to use only 2 ~ 4 input NAND gates. The inputs A, B, C, D, and E will be available from toggle switches. Any solution which uses 22 or fewer gates and inverters (not counting
the five inverters for the inputs) is acceptable.


texts:
How much power/intensity IR Diode should have to be seen from 30-50 meters by camera with IR pass filter? Must be a good point in a photo. Should be seen in a day light. Preferably with wide angle.

About power supply: 2-4 AA accumulators, should work at least a hour :)

Camera: I think 2-3 megapixel should be enough? Maybe more.


texts: Poor bandwidth after re-coupling an Ethernet cable

texts:
As part of an experiment I cut a Cat 5e Ethernet cable in half, stripped off a small amount of insulation on each wire and attached each pair of wires together with its own alligator clip.

There are four twisted pairs, so eight pairs of alligator clips are used.

Before cutting it in half I am able to transfer data between two computers using the cable and get ~940MBit/s which is close to the Gigabit/s speeds that Cat 5e is cable of.

However, after cutting it in half and reattaching the wires with alligator clips I get a 10x reduction in bandwidth and get a ~94MBits/s

What might be the reason for this and are there any techniques I can use to regain the original 940MBit/s speed.


texts: Is there a way to convert a 100Ω balanced connection to a 200Ω balanced connection without using two baluns? I have a 2.4GHz baseband that I want to attach to a front end, but the baseband has a 100Ω balanced connection and the front end has a 200Ω balanced connection. My first thought was to use two baluns to convert to a 50Ω stripline and then back to balanced connection, but I'd like to avoid this if there is a simpler way of doing it.


texts:
I am trying to drive 6 LEDs from an Esp8266 (esp201 break out board). Because of the Limit current of 12 mA the esp can do i want to use a  7way darlington Array to Power the LEDs.

I have programmed the esp for starters to blink only the gpios 4 and 5. No WiFi but Serial for debugging.

simulate this circuit – Schematic created using CircuitLab

Problem is that the esp restarts constantly. What i did to solve the Problem:

exchange esp
exchange uln
used a soldered breadboard to ensure  connections
used a 470 nf Elko between gnd and + 3.3
exchange Power supply

Nothing changed. The only thing that does work is to power up the esp and After that connect the uln. Then everything works like a Charme.

I gues My Problem has something to do with Power surge at startup but i dont know how to overcome.


texts: When dealing with voltages and amperage, which one can destroy your equipment when not properly matched to the proper device? Am I correct in thinking that attempting to charge a device with an adapter of the correct voltage but too low an amperage won't damage the device but will just take longer to charge?


texts: Constant Current, 1.5 amp, high voltage into variable load

texts:
I need to design a constant current 1.5 A circuit.

Input:  A 3.3 v, 3 mA, 1.5 millisec pulse.

Load: Detonators, with total resistance starting at 80 ohms and increases to 160 ohms in 1.5 ms.  Current must be continuous (NOT PWM).

Output: Current can vary between 1.4 to 1.6 A, ideally 1.5A.

Environment: Temperature varies between between 0 to 150 deg F

Max V required is V = 1.5 A * 160 ohm = 240 V.

240 V is too high for Constant Current (CC) IC's.  High volt BJT's & MOSFETs are very difficult to control at "low" 1.5 A current.  I can select a power supply of any voltage needed.  Has anyone else did CC with high current AND high v, pulsed for short time?  Thanks!


texts: I don't understand clearly why the ideal sources that the value doesn't match can't be connected

texts:
I'm studying recently Electric Circuits (9th edition) by Nilsson. In Chapter 2, an example bothers me.

simulate this circuit – Schematic created using CircuitLab

I don't understand why these above figures can't be permissible. (I know KVL and KCL, but I want to analyse these circuits with another physical meaning.)

In addition, I want to know what situations will appear in these circuits.


texts: How does an audio jack detect when a speaker is plugged in?

texts:
Some sound card audio jacks can now inform recent Windows OS's that an audio device is plugged in.  Anyone know how it does this?  I'm thinking it uses some kind of voltage comparator or resistance measurement.

This question was asked at Superuser.  My gut feeling is that the circuit is not as trivial as one of the participants is suggesting, but I'm a bit rusty on circuits.


texts: Transformer question regarding efficiency

texts:
Due to the question being discussed in length on the comment section, I would like to address my question further with a new post linking from the discussion here: Transformers confusion with output voltage and number of iron cores used

So with the help from this community, I understand that more iron cores means a greater magnetic permeability and less magnetic leakage. But does this mean that the magnetic field increases?

And assuming this is true, if we have a transformer with many iron cores in the center as compared to air, then the one with more iron cores will increase the current in the primary coils. So what I am failing to see here is, why is a greater magnetic field established (due to more iron cores used) increase primary current of the transformer?

I know there there is a magnetic field established when there is a current carrying wire, but I do not understand the relationship between magnetic field and current established. that is why does a stronger magnetic field established increase current in the primary coils is my key source of confusion at the moment with transformers.

Eventually I want to try to understand why more iron cores used increase the out voltage value of a transformer(secondary voltage). This is my understanding at the moment with many

$$\text{more iron cores}\rightarrow \text{stronger current in primary coils}\rightarrow \text{less current in secodary coils}\rightarrow\text{stronger secondary voltage }$$

I am not sure if this pathway to my understanding is correct, but I am stuck on the first arrow from more iron cores means stronger current in primary coils.

I would appreciate the help and clarification.

EDIT: This is somewhat what the experiment the professor was doing in front of the class today.


texts: Crossover for vintage 16ohm horn paired with 4ohm woofer

texts:
I'm in the process modernizing a 1960s Magnavox Astrosonic stereo console. I'm wanting to keep the speakers as they look to be in great shape. It's got two 12 inch woofers (581206-1) that test (via DC multimeter) at 4.1ohms so I assume the nominal impedance is 4ohms. It's also got two horns (580069-1) that test at 13ohms so I'm assuming they are 16ohms nominal.

I've also got a receiver / amp with these specs:

MAX Power Output: 200 Watt @ 4 Ohm
RMS Power Output: 100 Watt x 2 @ 8 Ohm
Tone Control: Bass, f=100Hz +/-8dB
Frequency Response: 20Hz - 20kHz
Frequency Adjustment: +/-10dB
Signal to Noise Ratio: >71dB
T.H.D.: <0.1%

I know I could just put a capacitor in front of the tweeter and wire them in parallel. Would that be safe with my amp and/or sound decent or should I get a proper crossover? If I need a proper crossover what should I buy. The speakers having different impedances is throwing me off.

Clearly, I don't know what I'm doing.


texts: Securing code on an AVR/Arduino and delivering updates

texts:
What is the best way to protect code flashed onto any AVR based device from reverse engineering?
What is an easy way to provide updates to end users to flash on their own without disclosing the code? (Is it with a bootloader that decrypts an encrypted image?)

Don't flame me for promoting DRM, I am in favor of open platforms--I am just curious how this would work.


texts: RS232/TTL converter with Arduino not recognized as serial device

texts:
My goal is a very basic one: I want to communicate from my microcontroller to my PC/phone via RS232.
I bought a TTL/RS232 converter like this.
And since my PC does not have a RS232 port I am using a RS232/USB cable like this.
I did the setup to my best of knowledge, but when I connect the USB end of the cable to my PC, it is not recognized as a serial device.
Therefore my question:
At what point should my device be recognized as a serial device (COMx) on a Windows PC? Would powering the TTL/RS232 converter be sufficient or does the microcontroller need to send something specific or just anything at all?
--
My setup and what I have done and tried so far:
The microcontroller I use for testing is a NodeMCU ESP8266 module.
I connected it to the converter like this:
GND --- GND
VCC --- 5V / 3.3V (which both should work with the converter module)
RX --- TX
TX --- RX
And then I hooked that up to my PC with the RS232/USB cable.
The schematic that came with the converter looks like this (I noticed however that the actual hardware I got does not have a 4x2 header):

There is plenty of code out there for writing data to a serial connection with Arduino. I tried writing to the hardware serial and also a SoftSerial with two safe pins on the ESP controller. I don't want to go into detail here, as long as I lack such basic understanding of the problem^^.
Sadly, I do not own an oscilloscope to watch the converter output.
Thanks for any pointers! :)


texts:
I am interested in this project and I am new to transistors and amplifiers. I have few concerns with respect to this project:

How to run the above given circuit with 5V instead of given 9V, what all modifications will I have to do?
I want to connect 2 speakers in this circuit, to have the stereo effect, how should I do that?
I didn't get the transistor mentioned above that is 2N3403 so the shopkeeper suggested that I take its equivalent i.e. BC337, will it work properly or do I have to change the resistors configuration?


texts:
I am designing a circuit for a strobe amplifier and am having some difficulty with the LED emitting light for longer than expected.

I am measuring the light out of the LED with a photo receptor module directly on a DSO and it tapers off over about 2ms from a 1us pulse.

I have attached the diagram of one of the circuits I have been working with, a basic emitter follower (the pulse is 0/5V from an AVR), but have tried other topologies, and also adding a shottky diode over the BE junction but to no avail.

Also the component numbers in the schematic are not exactly what I am using but representative. I have tried the BC337 and PN222A BJT's and an IN5817 shottky diode, and an unknown cheap red LED with approx. 2V drop.

I was hoping that someone would be able to explain why the long fall time for this particular circuit and perhaps suggest a solution.

Thanks in advance.


texts: Measuring/confirming voltage and current

texts:
new to the site and to electronics.
I just started learning about ohm's law and Kirchhoff's voltage law and trying to confirm values I am reading.
I have a simple circuit with a 9 V battery, 100 ohm resistor and red LED, the datasheet tells me forward voltage is 2.2 to 2.4. Checking with a multimeter the battery is 9.2 V and the resistor is 99.6 ohm.
First issue is voltage, when I measure the LED it has 2.33 V and the resistor has 5.8 V, this is 8.13 V not 9.2?
Then for current I believe we first get voltage (9.2 - 2.33 = 6.87) then 6.87/99.6 = 68.96 mA but when I measure I get 56.8 mA?
I don't understand why the numbers don't add up, can anyone help explain please?


texts: What kind of temperature sensor is this? What would be the best method for getting a reading from it?


texts: DIY Furnace cannot reach set temperature

texts:
I have built a tube furnace like the one in this video: https://youtu.be/YRZ7aQlqetE
The person in the video is able to reach 1100 C using an AC power supply. In summary, the furnace was made by wrapping an alumina tube (30 mm diameter) with ~7.6 meters of 22 gauge nichrome 80 wire, coating the wire in Dap furnace sealant, then finally wrapping the whole thing in two layers of alumina blanket. The furnace is controlled by an Auber Instruments SYL-2342P PID controller and a Holdwell 45GG20AF 2 pole 40 amp 120V coil contactor. There is a K-type thermocouple inserted into the tube. The diagram below depicts the wiring of the system, minus the alarms and the fuse.
The controller is programmable, and I programmed it like this:

C01-> 50 (starting temp in Farenheight)
t01-> 20 (ramp time in minutes)
C02-> 1832 (set temperature)
t02-> 15 (soak time)
C03-> 1832
t02-> -121 (stop)

Here's the problem: when I run this program, the furnace will hear up until about 1325 F then the temperature increase rate will slow dramatically until the controller stops the program. I am not sure if this is a problem with the furnace or the controller. Any help would be appreciated.


texts: Can a solar cell based lux meter produce useful readings for ultraviolet light?

texts:
I was reading the question Safety Guidelines for Ultraviolet LEDs? about ultraviolet exposure, and realized that a solar cell can probably detect this, since solar cells can also detect visible light, and I am now assuming ultraviolet, because it is higher energy than infrared. For some high producers of ultraviolet, it would be good to have some kind of measurement that can show when the ultraviolet radiation gets to the dangerous level.
I think my understanding of this came from the fact that all digital cameras are actually infrared sensors, but special filters in front of the sensor allows it to then sense color pixels. Carefully removing the filters changes the camera into an infrared camera.
Thanks.


texts:
To my understanding, most solar controllers use some form of PWM to output a desired current/voltage combination. These seem to often do some sort of DC-DC conversion.
This seems to be wasteful and inefficient however. During the off period of the PWM cycle, the sunlight hitting the PV panel is not used or stored for future use. So a controller using PWM at an 80% duty cycle can only be 80% efficient.

Is my understanding of the situation correct or am I missing something?

During the off period, could the PV power be diverted to charging another LC circuit so it isn't wasted?


texts: Turning on a salvaged computer power supply (Apple 8100 - SMP 220DB 8100 Series)

texts:
I salvaged a power supply out of my old Mac 8100 (it's an Apple 614 0012 200W Power Supply Power SMP 220DB 8100 Series). It looks like it will be good for my hobby projects (+5v, +12v, -12v ...negative voltage? don't know why I would want that, and +5v TRKL  ...don't know what that is. Trickle?) It has a 110/220 input - basically your standard computer supply.

I just don't know how to turn it on. I ran into this once before and thought the power supply was dead rather than it being managed by a power switch.

I'm assuming that one of the wires functions as a switch when grounded but since this is using house current, I figured I would ask before resorting to trial and error. Logic would seem to be that the blue wire (in the image below) if grounded to a black wire will turn the power on. Does this sound like a good guess?


texts: Purpose of serpentine routing on battery balance circuit PCB

texts:
I need a battery balance circuit, that I will either buy or design. I have seen serpentine routing between the load resistor and switching component in these photos (from china). In addition, it is not on the gate pin.

Could you please give some information about that?

I checked this question:Purpose of "wave shaped" PCB traces

I don't think I need "delay" and "Equalisation of length of pairs of traces". What could be the purpose of this routing?

Thanks a lot.


texts: How to solve Laplace and Poisson's equation using Monte Carlo simulation for a parallel plate cpacitor?

texts:
I know how to solve for voltage and field using Laplace and Poisson equation for a simple parallel plate capacitor. But I cannot get any idea on how to proceed with Monte-Carlo simulation using MatLab for the same.
Please help me.


texts: Will rapidly changing cycling an LED through different colors reduce lifespan?

texts:
I just purchased an RGB LED mechanical keyboard, where each key has its own color.

I was playing with the settings, and found one I like: each LED under each key rapidly cycles between colors.

It got me thinking - does rapidly changing an LED's color reduce lifespan, as opposed to keeping it at a constant color?


texts: My work directory in ModelSim is always empty. How can I resolve this problem?

texts:
I'm new to Verilog. I made a new ModelSim project and kept the default directory to work. Then I added .v (Verilog) files to the project. And after that I compiled the files. Compilation was successful. But even after that my work library is empty.

I don't know what changed, as previously I followed the similar procedure and files were added in work directory. Is this some problem of path/logical mapping?

I tried reinstalling the software, but the problem is the same. The following is the image after successful compilation of the software:


texts: What is the 'characteristic frequency' of a certain impedance?

texts:
I'm not familiar with that term. Could somebody explain it to me? Is it the frequency at which the phase of the AC current running through the impedance goes to zero?

Edit: Here is the context in which it is used.


texts: Switching regulator (TI LM2678) not working on load > 100mA

texts:
I am a (joung) programmeer and I recently began studying some electronics&AVR programming.

I am trying to use a step down voltage regulator (LM2678-5.0) to transform battery voltage (9/12V) into a suitable 5V. I am not using a simple LM7805 since this is part of a bigger robotic project, where I need to transform more than 1A, and it would be nice to spare energy (=less battery weight).

I built this schematic (photos below); with a 10kOhm load I get 5.02V; but as I attach a load to it, voltage drops. As example, as I attach a 20mA led, I get about 3V. I tried attaching a little (~400mA) motor, but it doesn't start (there's no voltage!).

Any suggestions? Thanks in advance

P.S.: inductors and capacitors has been chosen accordnigly to Texas Instruments online simulation tool


texts:
I want to control my home thermostat using an Arduino microcontroller. From what I've heard, it is pretty straightforward as the Arduino can be powered through the 24V that is coming to the thermostat and you can switch the A/C, heat, and fan through a relay. I don't want to mess directly with the thermostat without a little guidance from maybe someone who has done it before.

I have solid state relays on-hand, Arduino boards, and also any other components that are required can be purchased. Any pieces of advice or guidance for this project? How do I make the connections between the relays and the thermostat wires?


texts: VHDL: is there a way to create an entity into which constants can be passed?

texts:
Lets say we want to create a generic t flip flop counter, the structure of this kind of counter is perfectly repetitive, and you can synthesize one with arbitrary length just using a for generate

however the bound for that for and the length of the output is internal to the file, a constant, is there a way to sort of passing an argument when creating a component so as to define the length of the counter when creating the component instead of in the file?

here is the code of the counter i made

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.numeric_std.all;

entity counterTst is
port(
    enable: in      STD_LOGIC;
    clk:        in      STD_LOGIC;
    rst:        in      STD_LOGIC;
    output: out STD_LOGIC_VECTOR(3 downto 0)
    );
end counterTst;

architecture rtl of counterTst is

constant COUNTER_LEN:   integer := 4;

component t_ff  is
port(
    rst:    in      STD_LOGIC;
    clk:    in      STD_LOGIC;
    inp:    in      STD_LOGIC;
    t:      out STD_LOGIC
    );
end component t_ff;

signal  tin:    STD_LOGIC_VECTOR(COUNTER_LEN-2 downto 0);
signal  tout:   STD_LOGIC_VECTOR(COUNTER_LEN-1 downto 0);

begin

T_CHAIN_GEN:    for i in 0 to COUNTER_LEN-1 generate
    START_POS: if i = 0 generate
        FF0:    t_ff    port    map(rst, clk, enable, tout(0));
    end generate START_POS;

    POS_1:  if i = 1 generate
        tin(0) <= tout(0) and enable;
        FF1:    t_ff    port    map(rst, clk, tin(0), tout(1));
    end generate POS_2;

    POS_N:  if i > 1 generate
        tin(i-1) <= tout(i-1) and tin(i-2);
        FFX:    t_ff    port    map(rst, clk, tin(i-1), tout(i));
    end generate POS_N;
end generate T_CHAIN_GEN;

output <= tout;

end rtl;


texts: Power-on Reset for CD4017 gives unexpected results

texts:
In the circuit below, a 555 timer produces approximately 1 pulse per second, and the CD4017 counts pulses.  The initial state of a CD4017 is undefined, thus I need a reset pulse on power up.  In the circuit, that is a 4.7uF capacitor between Vdd and the Reset pin, and a 10k resistor from the Reset pin to ground.

As I understand it, when the power is first applied, the capacitor has no charge.
Until charged, it has effectively zero resistance, causing the Reset pin to go HI.  Then it charges, giving it high resistance, and the 10k resistor pulls the Reset pin LO.

That's the theory, anyway, according to various circuits I have studied around on other sites.  Since it is used a lot, I assumed it was a standard technique.

But what I see in practice is:

Turning on the power when the circuit and power supply has been turned off for awhile causes the Q0 LED to light briefly, then it quickly jumps to Q1.
If the power has been on, then I quickly turn it off then back on, the Q0 LED lights for a full second, then Q1 lights, the way I want it to always work.

Confession: the indicator LEDs are not actually as I have drawn them above.  I prototyped this circuit on a PAD-234A, which has eight buffered LEDs, and I just used those. One buffered LED circuit (from the PAD-234A schematic) is as follows:

Any ideas on why I see this behavior?
Is there a better power-on reset for a CD4017?


texts: I have a digital cable box that lives in a wooden cabinet under my tv.  I would like to use the remote with the doors to the cabinet closed.  It looks like an IR Repeater runs about $30+.  Can one be built easily for less?


texts: GNU Radio aliases occurrence dependent on data format

texts:
My setup is simply this:

I'll post some slides I made below which explain my issue.

Why doesn't the 700 Hz alias occur if I use the complex data format, but is shown for float data format? I suspect it has something to do with Euler's formula but can't really see it if so.


texts:
I can't saturate my NPN transistor!

Here is my circuit:

simulate this circuit – Schematic created using CircuitLab

The Vce is around 1.7 V, which is way above the saturation Vce of 0.3, meaning that I must be in linear mode right?

No matter what value resistor I try for Rb, the Vce doesn't change.

My LEDs are super-bright, 2.4v, 20 mA


texts: Filtering out everything below 12v on a car reverse light circuit

texts:
First of all I've like to mention that I'm by no means an electrical engineer. I'll try to explain what I mean with the title.

I have installed a headunit which has an option for a reverse camera. The headunit has a trigger wire which takes anything from 0 to 12 V.

I know an alternator makes it be 14.4 V approximately but for easyness sake we'll keep it at 12 V. If the trigger Wire notices a signal, it triggers the backup camera display in the headunit and a 12 V+ signal on a different wire.

The way the camera is now connected is as follows. I tapped in to the switched positive lead from the reverse lights and connected it to the trigger wire. The switched 12 V+ from the headunit, I connected to the camera positive lead. The camera negative lead goes to the reverse light negative lead. The issue with this is that BMW and possibly other brands as well, use a lower voltage test signal to see if the reverse lights still work (so they can show a notification on the dashboard) this triggers the trigger wire on the headunit and that will show the reverse camera.

This is not desired behaviour since I only want it to turn in when it gets more than let's say 12 V. I have a bunch of PNP and NPN transistors laying around as well as resistors and capacitors.

I'd like to avoid using a microprocessor to identify the signal. Is it possible to create the logic I'm after with just basic electronical components and how would I do this?


texts: Embedded system task scheduling for data aquisition on a CAN network

texts:
I'm struggling with the concept of how to schedule my tasks.

My Setup:
STM32F103 hooked up on CAN. Taking measurements with a Lidar V3 module comms via I2C, then distributing that measurement on the CAN

Interrupt 1 is a 1ms timer interrupt to initiate message send on CAN

interrupt 2 is active upon receiving CAN message

I also have to poll a register via I2C on the LIDAR unit to ensure that measurement has finished before I can then use I2C to read the distance register, code snippet shown below

        status = CheckLidarStatus();

        while ((status & LIDAR_BUSY) == LIDAR_BUSY)
        {
            status = CheckLidarStatus();
        }

What I believe is the correct flow that my program should take is shown below:

My main concerns are:

Does the flow seem a logical way in which to approach this?
If I prioritise the timer interrupt (rather than RX int) for CAN transmission, will this affect the CAN network negatively i.e. not dealing with the received CAN messages promptly enough?
If either of the interrupts are active during I2C comms, will it cause the I2C comms to "fall over"?
Is it acceptable to sit in a while loop waiting for the Checklidar status to come back as not busy, or is there a better way to do this?


texts: Verilog Reg File: Cant mix blocking and non-blocking assigment

texts:
I want to implement a blocking read to read the data as soon as it is written.
I am trying to implement a MIPS 1 pipeline and i need the data to be available in the same clock it is written.
The flips flops for intermediate variables between different stages work on positive clock edge. The write is on the negative clock edge.
If I want to read on a negative or positive i'll have to wait to the next cycle.
I am trying to write on the first half of the cycle and read on the second half. But if i read on the positive the FFs from the next stage won't get the value.

module registers#(
)(
input clk,
input reset,
input regwrite,
input [4 : 0] wr,
input [4 : 0] rr1,
input [4 : 0] rr2,
input [31 : 0] wd,
output[31 : 0] rd1,
output[31 : 0] rd2
);

reg [31 : 0] registers [31 : 0];

integer i;
initial
begin
for(i = 0; i < 32; i = i + 1)
    registers[i] = 0;
end

//READ
assign rd1 = registers[rr1];
assign rd2 = registers[rr2];

always@(negedge clk)
begin
if(reset)
    begin
        for(i = 0; i < 32; i = i + 1)
            registers[i] = 0;
    end
else
    begin
    if(regwrite)
        registers[wr] <= wd;
    end
end

endmodule


texts: What would happen if we provide a DC voltage to a transformer?

texts: I've read that you can use a transformer to step up or step down the voltage when the voltage is AC(i.e. the average value of voltage is 0). What would happen if the average value is not zero?


texts: Why is there a potential difference between neutral and ground (earth)?

texts:
I was surprised to find that bridging neutral and ground in a socket at home tripped the RCD. Measuring with a multimeter, there is indeed 0.1 V between them. If the RCD trips at 30mA that would mean that the wiring in the house must have resistance lower than 3 ohms. (Sounds likely if household wiring is around 0.01 ohm/meter.) So the questions are:

1) why is there a p.d. at all?

2) isn't it a problem for doing electrical work, since switching off the circuit breaker for the ring only disconnects the live wire, meaning the RCD can still trip the whole house if the neutral and ground wires touch?

EDIT: since there are different earthing standard apparently, this question relates to the UK and to a normal urban setup (2-wire 1-phase mains). Also, the live wire is disconnected on the ring. I think the RCD trips because the (small) potential difference between the neutral and earth creates a small but big enough current through the neutral wire, which is not balanced by current in the live wire.


texts: How current flows in a circuit as per Kirchhoff's law if the voltage dropped = voltage applied

texts:
According to the Kirchhoff's law the voltage drop is always equal to the voltage applied, then how come the current even flows in the last part of the circuit?
For example if in a circuit which has a 9 volts battery, there is a resistance which drops the current from 9 volts to 0 volts(i.e., 9 ohms), then if we look at atomic level then the electrons flowing in after the resistor will repel the positive terminal because of their net charge.
I know that I am misunderstanding something but if you know the correct theory then please answer.


texts: Question about calculating the rms noise from sampled DC measurement

texts:
If I want to estimate the rms noise of a DC signal, like a DC offset reading of an analog transducer sampled at a certain frequency.

So imagine I used the anti-aliasing filter correctly and and fed the DC output to a a 16-bit ADC and sampled it for 30 seconds and recorded samples of this DC analog signal.

Now since we can plot the data or make analysis of this logged DC by using the samples, my question is about estimating the rms noise of this sampled data of the DC input.

I call the sampled DC signal as s[n] or simply s. The mean of the signal as I call mean(s). And rms of the signal is rms(s) and standard deviation of the signal as stdv(s).

Now if I want to estimate the rms noise which one below is more convenient to use and why?:

1) rms noise = rms(s-mean(s)) ? (Should I subtract the mean value even if I short the ADC inouts+)

2) rms noise = stdv(s) ?

Are the above equivalent? If so, which type of standard deviation is this?


texts: How to calculate R,L,C on a bandpass filter?

texts:
As part of a project I'm doing for the class Signal and Systems Analysis, I'm given the following:

With A=10, T=0.25ms and To=1ms.

I am then asked to:

After reading a lot, I think that I should use the RLC Bandpass filter, but I'm not 100% sure. Also, the main problem is that I do not know how to calculate R, L, and C for the filter, knowing only the entrance signal x(t) and the frequency of the output.

Does anyone have any idea of how to solve this?

Thanks a lot


texts: Replacing a Capacitor on an Onkyo HT-R960 A/V Receiver

texts:
I have an Onkyo HT-R960 receiver that's been acting very flaky for the past couple of months.  I've had to let it warm up for several minutes before being able to use it.  I would also have to turn it off and on after it warmed up for it to serve the audio.  If I didn't it would sound as click and pop (static) and then go into protective mode (auto-shut off) if turning the volume up too high.  Once it warmed up and I turned it off and then back on it would be fine.  At the moment it's still clicking and popping, but no amount of warming it up seems to get it to work.  I can, however, force it to go into stereo and it plays audio fine on two-channels only.  Nonetheless, I've opened it up and it appears the main two capacitors have this tacky black goo on them.  The dimple on the top of the capacitors isn't expanded as one can see though.  At first I thought this was some sort of insulating material for these capacitors and it was intended.  Now I'm not so sure and I've gleaned from several places that it could be leaking from the one or more of the capacitors.  Upon further inspection, it does appear to possibly be originating from the capacitors.  I won't be able to truly tell unless I remove them.  I guess that's next?

My questions are the following:

Where to get replacements for these if they should get replaced?  From what I can tell this would be an exact replacement:  https://www.ebay.com/i/183199809718

However, I've seen much cheaper, but higher voltage versions of these and wonder if those would be Ok:  https://www.ebay.com/i/182068444181

Should my next step be to remove these and determine if the goo is truly leaking from them?  I've replaced capacitors before on other electronics, but I've never heard of a failure with them other than the proverbial dimple expanding to show a failure.

I'm including and image of my capacitors on the main board and a link to the service manual that has schematics for this board.  For reference the capacitors are C6901 and C6902 when looking at the manual.

My thanks in advance for any advice.

Service Manual PDF for HT-960


texts: Comparing luminosity of LEDs of different units

texts:
I'm currently trying to compare two LEDs with respect to their perceived brightness:

Amber Cree Part# XPEBPA-L1-0000-00D01, 107 Minimum Luminous Flux @ 350mA

Royal Blue Cree Part# XPEBRY-L1-0000-00S01, 650mW Minimum Radiant Flux @ 350mA

Unfortunately, their perceived brightness is given in two different units. Is there a possibility to convert the Radiant Flux into Luminous Flux?


texts: Looking to get started with ARM microcontroller development on Linux

texts:
I am looking to get started in developing for ARM microcontrollers on Linux.

Keep in mind I really enjoy the low level.  Right now I have some experience with PIC16F series and 8 bit AVR.  This is on the assembler level.  I much prefer the PIC over AVR right now because it has rock solid debug and hardware dongle support for Linux everything with AVR feels like a hack.

Anyone have any suggestions on development boards and tools that will work well for Linux that will not cost huge amount of money as I am just a hobby guy.

If you need any more info I would be happy to give it just ask.


texts: Filtering capacitors and inductors on power supply, how to choose and size?

texts:
I know this is fairly simple, and I get why these components are there.  However, I do not fully understand why the certain values are picked and what the end filtering result is.

Is the inductor in series or parallel with the capacitors?  It seems to be in series with them to ground, but parallel to the Vin pin (one end connected to Vcc, other to caps and Vin).
Is this a series LC filtering circuit?  How would you determine which frequencies are being restricted?  I know the basic equations, but not necessarily how to apply them.
I understand that the caps shunt AC to ground, and the inductors 'block' AC with high impedance.  The end result is that the L and C are filtering AC noise, but why are these particular values chosen?
Why are several caps used in parallel, and why is one in front of the inductor?
On the output, why are two capacitors used, one that is 50V and one that is 25V rated?


texts:
I'm studying the following circuit

The image is explicit but as you can see the input measured in the upper terminal is a square wave with \$E_c\$ and \$-E_c\$ as levels.

Now I also had no trouble understanding that if \$R_B \leq \beta R_C\$ when the square wave is in the positive half-cycle we have saturation and when it is on the negative half-cycle we have cutoff situation.

Now in saturation we will (because the junction voltages are zero) an output voltage of zero. That is correct with the figure. However when we are in cutoff, applying KVL to the output mesh leads us to

$$U_{CE}=-E_c$$

because currents can be neglected.
That however is not concordant with the figure which shows $$U_{CE}=E_c$$
Why is that? What am I missing?


texts:
I have a video signal coming from a composite video out (we can ignore audio at this point). Products such as EasyCAP can convert such signal to usb differential(d+/d-) signal. Arduino/raspberrypi can process the incoming signal voltage from usb and modulate the LED accordingly. Modulate LED light to transmit the digital usb signal (d+/d-) to the receiver end. At the receiver end the generated optical signal needs to be converted back to equivalent voltage, this voltage will be fed to a usb-->composite video converter to play on the screen in real time. (At Receiver end is a PD to convert light to voltage. Again, for processing either arduino/raspberry pi.)

Now, From usb i have d+ and d- differential signal coming out. How do I achieve equivalent optical signal from it?
How do I establish the half duplex system (any code)?

Thank you in advance.


texts: Using an unamplified piezo in a mic-in jack

texts:
it's my first time working with piezos and I'd like to use one as an input to my iPhone via the microphone port to allow my app to detect vibrations.

in order to do this, I was thinking that I'd use a splitter to separate the headphone and microphone channels for my iPhone, then plug my piezo directly into the microphone port.

first of all: would that work? second of all: is there any danger that I'd harm the microphone-in of my iPhone?

thanks!


texts: Why does power dip during a lightning storm?

texts:
If lightning were to strike power lines, wouldn't you expect it to increase the power, and hence your room lights get brighter?

Why do they go dim for 1 second at a time?


texts: Questions About Charging Lithum Ion Batteries

texts:
I have a few questions about charging Lithium Ion Batteries aka a collection of cells...im learnin...lol

1) I am looking to setup 14x18650 cells to make a 51.8v module in series. I know I need its best to use a BMS (purchased). I also got a smart charger that is designed to charge 14s modules. Can I use both at the same time? Or will they interfere with each other?

2) The charger in question is 52v but it is also rated at 3A. Am I missing something. I understand that to charge a 14s you would basically do 4.2v x 14 = 58.8v. But I thought in this case you would only charge it at standard amps of in this case 2.2A / 2 = 1A? Wont 3 amps be way over?

This project is for learning mostly so I am not planning to use this in real "production" capacity.

Thank you for your assistance!


texts:
I have two options for power sources for my board, which simply has an ATMega on it --- one is a 24 VDC source going into a switching regulator that supplies the board with 5 V. Another source is via a USB Bus using an FT232R that could also supply the board with 5 V. Is there a way I can ensure that only one or the other powers the board and not both?

Or could both these be plugged in parallel and have no effect on the circuit? (I find that hard to imagine)


texts: Root Locus, Gain in Feedback Loop. Need help

texts: So this is the system for which I have to draw a root locus if 'K' changes from 0 to infinity. The problem for me is that root locus is drawn for open loop transfer function but 'K' is in the feedback loop. I'm guessing that there is a way to get K in open loop transfer function but I've tried everything and just cant do it. I have no problems if K is in open loop tho. I appreciate any help.


texts: I have designed a tapered slot antenna operating in C band on an FR4 substrate . However , despite rigorous simulations the response has shifted by nearly 1 Ghz . I was wondering if extra substrate in the TSA has caused this?


texts:
I've designed a fairly simple circuit with some shift registers (3 output en 1 input).
In the circuit, I've connected the inputs from the input shift register to pin connectors on the board (so I connect a NO switch and pull the pin to ground when pressed).
The pin from the shift register is also connect to V+ with a 10K resistor in between.
I've added the schematics from which I had a PCB made.
The issue is that, when a button is closed or the corresponding pin is grounded (in the schematics, one of Switch 1-8 connected to a 74HC165D), the first 74HC595 quickly heats up and eventually burns out.
Nothing else is connected at this point , only 5v and ground and the 5 wires from the arduino (the second power-port and 'chain' ports are meant to chain the board together). As a test I simply put a wire from a 'Switch Port' to Ground.
I'm a real beginner and always take on projects that are a little over my head...
I would really appreciate if someone can tell me about the mistakes I made designing this circuit.

This is the resulting PCB (created in EasyEDA)


texts: Storing a secure key in an embedded device's memory

texts:
I am working on an embedded device which send/receive data and stored them in ciphertext mode (encrypted mode).
Now what's best approach for storing keys (I used ARM CORTEX M series MCU)?

1-Storing keys in the SRAM memory and in each booting sequence, inject keys to the embedded MCU and store them in the SRAM memory.
It is best way I think,then when MCU sense penetration (with tamper sensor or ...) it can erased SRAM quickly and reset itself.
Disadvantage: if attacker success to pass tampers and access to device, how safe is SRAM memory (against code mining). I can't find  any security ability for this memory in MCUs.

2-Generate keys and stored them in the flash memory in programming MCU.
MCU flash memory's support CRP (code read protection) which prevent from code mining and with assist of its internal AES engine and RNG (random number generation) engine we can make a random key and encrypt flash memory and stored that random key in the OTP (one time programmable memory -a 128 bit encrypted memory), then in code execution we decode flash memory with RNG key and access to initial key and codes.
Disadvantage: Keys stored in a non volatile memory, tampers will be useless and attacker have a lot of time to mine keys.

3-Stored key in the EEPROM memory,combination of 2 above approach, key stored in the non volatile memory but when tampers sense penetration EEPROM is erasable.

I consider LPC18S57FBD208(cortex m3 with 1MB of flash memory, 180MHZ, 136KB SRAM, 16KB EEPROM and a TFT LCD controller which i need to drive a 7" TFT LCD and AES 128 bit crypto engine) for that is there any other better suggestion?


texts: How does this negative voltage generator work?

texts:
I managed to fry a piece of moderately rare equipment due to connecting it to the wrong voltage power supply, and I'm now trying to diagnose what's wrong. Luckily, reverse engineered schematics are available (http://electrickery.xs4all.nl/comp/px8/doc/f10pa.pdf).

I've managed to identify one possible problem; there's a -12V power supply, which is actually generating -7.8V. Circuit below. (I didn't draw this. It's using US-style zigzag resistors; note that L7 is actually an inductor.)

So I'm rather puzzled as to how this works. I can identify the general principle: the two Schmitt triggers form an oscillator; this combined with the L7 inductor produces voltage spikes; C9 decouples this; D17 grounds the positive spikes but lets the negative ones through to charge C10; C31 is a smoothing capacitor.

However, the closest thing I can find to a voltage reference is the potential divider / transistor arrangement at Q13 / R86 / R83. I would expect the divider to turn the transistor on if the output voltage is too great, causing C10 to be discharged and so lower the voltage (lower in this case meaning 'towards zero', because the output voltage is of course negative).

Except the potential divider appears to generate about -1V when the output voltage is -12V, which is higher than the turn-on voltage of about 0.6V. But it produces -0.6V when given the -7.8V I'm seeing, which is... suspicious. Also, why is the collector connected to the oscillator circuit and not to ground?

So my questions are: how does this all actually work, and how could this circuit ever have generated -12V?


texts: Selecting an amplifier - a PA or LNA that seem to have similar gains and P1db

texts:
I am using an SDR that outputs a maximum power of -25dBm. I need about 15dBm to go into the Tx antenna.
I am looking at a PA and an LNA that have similar P1db points, but the LNA has a much better noise figure. I know that LNA is for receiving, but looking at the data sheet, it looks like it will be a good PA as well.
https://rfbayinc.com/products_pdf/product_1_584.pdf
https://rfbayinc.com/products_pdf/product_1_611.pdf
What am I missing?


texts:
Hi, can anyone describe the operation of this circuit for me, in particular what the 10 ohm resistor is for.

It is meant to achieve a very high level of current through the LED.

Many thanks,

John


texts: A transmission line with continuously varying impedance, how would reflection occur in this case?

texts:
Alright folks here it is, another transmission line question that has been bothering me. I understand the case where there is an abrupt change in impedance along a transmission line that leads to reflection of portion (or even all) of the signal.

Now, what is bothering me for a while is the case where we have a transmission line who's impedance varies in a predictable manner over its length. Lets suppose that we have a PCB trace who's characteristic impedance depends on it's width as per physics. Now suppose that this width is increasing linearly as the signal travels on it which leads to a continuosly linear change in it's impedance. I expect that signal would be reflected in this case too but continuously! But what I cannot imagine is how would the reflection look like in this case on the transmitting end and what the signal would look like on the receiving end. Besides this, how can one mitigate this type of impedance mismatch, I suppose that getting the correct receiver termination would be tricky in this case. hmmmmmmm...


texts:
I have a op amplifier for which I want to calculate Vout depending on Vin.

The circuit looks like this:

I know that with a circuit that just has ground connected to + of the amp, i can just calculate KVL: V1 = R1*I1+Rf*If+Vout but with this amp, there is also resistors on the plus side of the amp to include in the calculation. I know that I should consider the op to not let any curren through. Therefore I think that I can use KVL on the plus side as well, so that I get two KVL-equations.

My question is now, if I have V1 = R1*I1+Rf*If+Vout and V2=R2*I2+R3*I3, how do I put them together?

I think that I can assume I1=If and I2=I3, if that helps.


texts:
I painted the currents, used the first Kirchhoff's law and got the expression:

Next, I need to find the voltage transfer coefficient (Ku), that is, the ratio of the output voltage to the input voltage, but I do not quite understand how to do this due to the fact that there is dU(out) and just U(out)


texts: Is RF Transformer Impedance Significantly Affected by Wire Size?

texts:
I'm building a Softrock Ensemble III HF Receiver. The online instructions are pretty good, but have a few remnants from an earlier version that no longer apply. So, despite the discussion about the difference between #30 and #26 wire, when I saw that the two hanks of magnet wire were the same color I assumed they were the same size (in the RXTX kit they are different colors). When I wound T2 I used the #26 wire (which was a very tight fit) instead of the #30 wire. You can see the partial circuit diagram and the construction details for T2 here (scroll down to the Summary Build Notes, then click "Install BPF Input Components"). Do I need to remove T2 from the circuit board and rewind it with the smaller wire?

EDIT (adding details of the transformer, repeated from the linked page):

The transformer is 4 bifilar turns on a BN43-2402 ferrite transformer core. It's specified as 23.04µH for both the primary and the secondary. It's the RF input transformer; the primary connects directly to the antenna jack. The receiver covers the HF bands, 1-30 MHz.


texts: What are the the advantages of a switched capacitor filter over a digital filter?

texts:
The main advantage that switched capacitor filters seem to have over digital filters is the potential to achieve a high dynamic range, since the signal does not have to be quantized.

As discrete time filters, they share the digital filter's frequency aliasing problem, and may need multiple clocks at different frequencies as well. Digital filters seem more flexible and easy to design, and analog filters are still needed to deal with frequencies above the Nyquist limit.

What other advantages do switched capacitor filters have over digital filters?


texts: How can a power adapter have higher output current than input?

texts:
I have a USB power adapter for a speaker.  The specs on it say:
Input: 100-240v-50/60Hz  0.4A
Output: 5V 2000mA
Question:
Isn't 2000mA the same as 2A?
If so, how is that possible?


texts: Interrupt fails to change variable, how so?

texts:
Problem was virtually undebuggable, the interrupt that was changing a variable would randomly fail to do so, with no apparent pattern; within interrupt code variable would change but outside of it the change is essentially reverted back to previous state. It's a regular variable so it's not double-buffered. Marking it as volatile had no effect (besides making the code run slower). I've already worked around the problem, but phenomena is still there nonetheless. Also, my chip is Atmega644 and language is C.

I have narrower down the problem to a following code: the interrupt was firing during the execution of code that was also writing to that variable. It checked for pin state, and depending on it would either set or clear a bit from that variable. I resolved the issue by putting that code in the interrupt as well, which left interruptable code with not a single place where that variable was written - only read.

The code is substantially long, so I only provide relevant snippets (the rest of the code doesn't even deals with related variables):

#define BIT(x) (1<<(x))
#define BITSET(x,y) ((x)|=(y))
#define BITCLR(x,y) ((x)&=~(y))

//Interrupt snippet:
if ( PINB & BIT(PINB0) )
    BITSET( display, BIT(DSPL_PWR) );
if ( PINB & BIT(PINB1) )
    BITSET( display, BIT(DSPL_ACT) );

//Main code:
if ( PIND & BIT(PIND2) )
    BITSET( display, BIT(DSPL_ACC) );
else
    BITCLR( display, BIT(DSPL_ACC) );

<...>
leds_display = 0x00;
switch ( roll )
{
    case 0:
        leds_display |= display & BIT(DSPL_PWR);
        break;
    //etc.
}
PORTA = leds_display;

However, that is but a crutch-fix. It works that way, but it should've worked the way it was. Changing a variable is atomic operation, so it can not be interrupted mid-action. My guess was that it was due to optimization magic, but then volatile would have changed the behavior. And even then, even without volatile marker, the code may have ignored the change the first time it ran (it's not critical for it to be real-time up to date), but the next iteration would have recognized the change. This leaves me puzzled about nature of the phenomena.

Anyone knows anything about it? Or is it just a compiler bug?


texts: Thermistor is accurate on Arduino, but is off by 10 degrees F on wemos d1 mini

texts:
I'm new to electronics and followed a simple thermistor tutorial which worked flawlessly. It uses Arduino Uno, a 10k thermistor and a 10k resistor.
Now I'm trying to use the exact same circuit except with a Wemos D1 Mini, but the temperature is now about 10 degrees Fahrenheit higher than when I was using the Arduino.
The only difference I can see is that the Wemos D1 Mini uses 3.3V instead of the Arduino's 5V. Could this make a difference in the temperature reading? However, if I use the Wemos D1 Mini`s 5V pin, the temperature is about 60 degrees F off so I'm not sure what is going on.
What might cause this 10 degree difference and what can I do to fix it?
Circuit:

simulate this circuit – Schematic created using CircuitLab
Code:
void setup() {
  Serial.begin(9600);
}
float currentTemp(int tempPin) {
  int tempReading = analogRead(tempPin);
  double tempK = log(10000.0 * ((1024.0 / tempReading - 1)));
  tempK = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * tempK * tempK )) * tempK );       //  Temp Kelvin
  float tempC = tempK - 273.15;            // Convert Kelvin to Celcius
  float tempF = (tempC * 9.0)/ 5.0 + 32.0; // Convert Celcius to Fahrenheit
  return tempF;
}

void loop()
{
  double tempF = currentTemp(A0);
  Serial.println((String)"tempF: " + tempF);
  delay(1000);
}


texts: FIFO for spartan 3AN : no storage on board but ok in simulation

texts:
I made a FIFO using the Core Generator and I'm trying to implement a code that use it...

1) By putting the switch (T9) ON, I start transmitting some datas to my fifo (Here H-e-l-l-o for test)

2) By pressing the button T16, I read the FIFO

The code is working on simulation but not in implementation... Here's my simulation result :

The lines are in this order :

CLK
SWITCH
BUTTON
RST
No need
No need
No need
Data_out

As you can see, it sends a zero then a 72 (H from ASCII code because I'm sending data using RS232) then 101 (e) then 2 times 108 (l) and then 111 (0) is reapeted because the fifo is working in a way that if it's empty, it's sending the last value so it's working fine.

Here's the result I have using putty (an RS232 reader) and by pushing the button T16 a lot of times :

Here's a part of my code, I can put the zip file if you needed, just ask it in comment.

The part where I generate the data into the FIFO :

process(clk)
begin
if rising_edge (clk) then
if SW_T9 ='1' then
        if cnt = 10 then
            wr_en <= '0';
        elsif cnt = 11 then
            DATA <= "010010000000000000";--H
        elsif cnt = 12 then
            wr_en <= '1';
        elsif cnt = 13 then
            wr_en <= '0';
        elsif cnt = 14 then
            DATA <= "011001010000000000";--e
        elsif cnt = 15 then
            wr_en <= '1';
        elsif cnt = 16 then
            wr_en <= '0';
        elsif cnt = 17 then
            DATA <= "011011000000000000";--l
        elsif cnt = 18 then
            wr_en <= '1';
        elsif cnt = 19 then
            wr_en <= '0';
        elsif cnt = 20 then
            DATA <= "011011000000000000";--l
        elsif cnt = 21 then
            wr_en <= '1';
        elsif cnt = 22 then
            wr_en <= '0';
        elsif cnt = 23 then
            DATA <= "011011110000000000";--o
        elsif cnt = 24 then
            wr_en <= '1';
        elsif cnt = 25 then
            wr_en <= '0';
        end if;
        if cnt <25 then
            cnt <= cnt+1;
        end if;
        end if;
end if;
end process;
end Behavioral;

Here are my errors (only during Synthesis) :

  WARNING:Xst:2211 - "D:/Users/.../TOP_MODULE.vhd" line 135: Instantiating black box module .

  WARNING:Xst:1710 - FF/Latch  (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.

  WARNING:Xst:1710 - FF/Latch  (without init value) has a constant value of 0 in block . This FF/Latch will be trimmed during the optimization process.

No important warning as you can see (I hope I'm right)...

My question is : Do you know why I don't have the same result in simulation and on board?

Don't hesitate to comment and ask me question, it's really important for me to solve this problem...


texts: dsPIC33 oscillator and timer configuration

texts:
I configured my dsPIC33 oscilator to operate at 60MHz using a 15MHz external crystal. So, to confirm the configuration, I did a routine to oscilate a pin, high and low, with a 2us period. But it seems do not work, a delay of 1us appears when I try to see it at the oscilloscope. instead of 1us, it became 2us, when I put delay of 2us, the delay is 3us. I will put here the code and the image of the oscilloscope.
This is the oscilator configuration:
void oscilator_configOscilator(){

  CLKDIVbits.PLLPRE = 1;   // N1 - 2
  CLKDIVbits.PLLPOST = 0;  // (N2/2) - 1
  PLLFBDbits.PLLDIV = 46; // M - 2

  RCONbits.SWDTEN = 0;

  CLKDIVbits.DOZE = 0x000;
  CLKDIVbits.DOZEN = 0;

  // Initiate Clock Switch to Primary Oscillator with PLL (NOSC=0b011)
  __builtin_write_OSCCONH(0x03);
  __builtin_write_OSCCONL(OSCCON | 0x01);

  // Wait for Clock switch to occur
  while (OSCCONbits.COSC!= 0b011);
  // Wait for PLL to lock
  while (OSCCONbits.LOCK!= 1);
}

This is the code to generate square wave with 2us of period:
 while(1){
  PORTBbits.RB1= 0;
  time_delayMicroseconds(1);
  PORTBbits.RB1= 1;
  time_delayMicroseconds(1);
  }

This is the code of timer configuration and interruption:
void time_ConfigSincTimer(void){

  T1CONbits.TCKPS = 0;
  T1CONbits.TCS = 0;

  PR1 = 59;

  IEC0bits.T1IE = 1;
  IFS0bits.T1IF = 0;
  T1CONbits.TON = 0;

  ticksMicrosecond = 0;
}

void time_delayMicroseconds(Tuint16 timeUs){
  ticksMicrosecond = 0;
  TMR1 = 0;
  IEC0bits.T1IE = 1;
  IFS0bits.T1IF = 0;

  T1CONbits.TON = 1;

  // wait
  while(ticksMicrosecond < timeUs);
  IEC0bits.T1IE = 0;

  T1CONbits.TON = 0;
}

void __attribute__((interrupt, no_auto_psv)) _T1Interrupt(void){
  IFS0bits.T1IF = 0;
  ticksMicrosecond++;
}

This is the measure at the pin RB1 when a delay of 1us is used:

Please, Am I doing something wrong ? Why the period became greather by 1us ?


texts: Liquid Tape for protecting exposed electronic components

texts:
I recently found the liquid tape LTB-400 made by Garnder Bender and was wondering if it's Ok to use it to cover IC chips for ESD protection? The circuit board is not placed in a housing, it's sold as a standalone unit.
I have used MG acrylic conformal coating before but was wondering if this will be an acceptable alternative method?

Few advantages of the liquid tape:
1-You can peel it off if you need to re-work or replace the onboard IC.
2-It has 1400v/mil dielectric protection. So a 10 mil layer adds up to 14k volts protection.
It looks like it's a neutral cure.
Any comments or suggestions is appreciated.

Thank you


texts:
I have added the problem with its solution.

I tried applying Mason's Gain Formula which led me to the same result and it should have as Transfer Function is unique.

Is there a shorter way to get Transfer Function similar to the below trick we have for Companion form or through some other manipulation ?


texts: Controlling actuators - SPI - I2C - OneWire

texts:
I never worked with one of the above methods but for my next project I have to. I already read a bit about it but would like to have some user experience data.( I ordered them already to test it myself as well)
I am using an Esp32 as a mqtt client. It resolves the data and controls actuators (mosfets). Right now it simply uses the io pins but we need more pins/want to add features like Ethernetcontroll over SPI or external PHY Module (LAN8720)
For that we thought about adding either some kind of io expander via SPI or I2C. Another idea would be just to control them over single-wire. Everything is fairly easy to program in arduino so I doubt there will be a problem.
What I would like to know is, if I would notice speed/delay from getting a signal to switching the mosfet depending on the used data transfer method. The wires are all pretty short and we have about 16 actuators so I would use 2x8 expanders(MCP 23S08-E/P /MCP 23S09-E/P or 2 OneWire 8 channels(DS2408)
Will I notice a difference in speed if I switch actors depending on the method?
Will I notice a difference in speed if I used Ethernet over SPI-Lan Module vs external PHY
How easy are they to programm ? What is the best,easiest for the ESP32 ? What is the fastest ?
Thanks and Greetings !


texts: Using a potentiometer to control greater resistance

texts:
This is more a theoretical question: Let's say we use a potentiometer as a variable resistor. We can set it from 0% (0Ω) to 100% (let's say 1Ω for simplicity).
Using this pot we can reduce the total range of resistances covered by the 0% to 100% by adding a resistor in parallel. (This results in a non-linear relationship between the position of the wiper and the resistance, but that is fine.) For instance adding 1 ohm resistor we get a maximum of 0.5Ω.

Now I was wondering, is it possible to have a circuit using only resistors to control a larger range of resistances with this potentiometer? (Having 0Ω at 0% is not a requirement!)
My gut feeling is that this is not possible, but I did not manage to prove it.


texts: Conditions for Thevenin and Norton non-existance

texts:
It's not clear to me when a Thevenin or Norton equivalent cannot be produced for a given linear circuit. Can anyone help me with a clear definition?

Thanks!!


texts: How to know if test points can introduce EMC problems

texts:
After getting some advices from my PCB manufacturer and from people here, I decided to change the PCB design I'm working on so the PCB could be tested using a bed of nails.

To do so, I added test points on all nets. Since the components are on the top only and that some tracks were also only on top, I had to create vias to connect these tracks to some large pads (1.2 mm) on the bottom. It is where I started to get worried that I was actually creating some net antennas everywhere on the circuit... My worries didn't really get better since some test points are on the switching node of power supplies (from 200 KHz to 2 MHz).

The PCB we are talking about :
 - 4-layer PCB (a few power supplies, a battery charger, connectors to screen and other accessories)
    only surface-mount components
 - no impedance control on any tracks

My questions are:

Is it a bad design choice to add vias (not connected to anything on the bottom side since it is only a test point) on switching node and other "high frequency" ( < 10 MHz) traces? The vias are to test traces existing only on top using a test point on the bottom.
Does it exist a rule of thumb to know what a maximum acceptable net antennas for a signal working in some known working frequencies?
Should I just stop worrying about it?

EDIT:
Maximum "net antenna length" to be able to place a test point is about 3 mm...


texts: Why some newer LCD panels have 120Hz refresh rate, and not 60Hz? How we can determine what is the most optimal resolution to use to display content on our LCD, does it depends of our CPU power or GPU power? What we get with that 120 Hz and even higher refresh rate frequencies?


texts: Protecting microcontroller digital output pin from ESD, reverse connection, and other possible user error

texts:
I want to protect an output pin from ESD, reverse connection, and other possible user error that might cause damages to my circuit. This pin output pulses depend on the amount of water passing through a pipe and is to be read by the user. The circuit must be of very low consumption because it is supplied by a batteries that must work for years.

Does anyone have an example circuit to start with?

After reviewing different circuit, I decided to use the following circuit to optically isolate my circuit from the outside. Do you have any suggestion to complete this circuit?


texts: Voltage across current source in an open circuit

texts: My question is after steady state(ie. when capacitor is fully charged and behaves as an open circuit) is achieved what would be the potential difference across the dependent current source? How do I find it?


texts: Is it true that the ATtiny AVRs have no hardware support for multiplication? It seems to work fine as I do multiplication in my code. I've also included math.h and have a couple of sin() and cos() calculations. Am I running into some huge 800-cycle penalty for these calculations, does anyone know?


texts:
I have a LCD i want to use for a project but still can't get it working on a breadboard.

I have used LCD's before so I'm familiar with them, this one however has something i haven't seen before.

From my experience pin 15 is usually LED+, in the datasheet of this LCD it says that pin 15 is Vee and is a negative voltage output.

I read somewhere that Vee controls the contrast of the LCD, but that would be strange because according to this datasheet the contrast is controlled with pin 3.

If i connect everything and apply power i see this only:

Anyone any ideas?


texts:
I want to build connection like this. Is it safe? I want to put fuse in the circuit. Where should I put the fuses before or after converter?

There is no any fuses in the system yet. I am using this converter (sunsky-online.com/product/…) I use 30A model and (continental.sg/step-down/products/…). For wiring from battery I use 12AWG wire for 30A converter and 16AWG wire for 12A converter.

Thank You.


texts:
My PCB must be able to connect to and power another PCB. I found that when I first connect them the other PCB draws enough power (peak of about 60mA) to dip the voltage on my PCB for about 80us and causes my microcontroller to reset.
I want to add a capacitor (or a few) to my PCB to keep this from happening.
Any ideas on how to calculate the right capacitor value?
See picture for an oscilloscope trace of the voltage drop:


texts:
simulate this circuit – Schematic created using CircuitLab
There is also the resistance of the Mosfet which is equal to 0.25(Ohm) I just didn't know how to add it to the circuit. We're gonna call it Rdson.
First question says: Calculate Ids that passes through the transistor.
Vcc - rIds - Rdson x Ids = 0
Ids = 12/ (0.25 + 1.25) = 8 A
Second question says: Calculate VDS(max)
Vds = Ids(r + Rdson) = 8(1.5) = 12v
That's what I don't understand. Why the book included r in calculating VDS? Isn't it supposed to be:
Vds = Ids x r
Did the book make a mistake here?
Also, is VDS(max) the same as normal VDS?
My problem: How VDS(max) is calculated in this circuit? Is the way the book solved it correct?


texts: 16 segment display datasheet interpretation

texts:
I'm looking at the datasheet for Kingbright PSA08-12EWA.

There appears to be two voltage inputs and no DP connection. Am I mistaken? If not, why would they do that?


texts:
I took the circuit below from an App Note from Texas Instruments, and I decided to study it. My questions are about the comparators U6A, U6B.

About U6A: The inverting input is set to 0.7 V because of the diode D12. At the non-inverting input, the voltage is defined by the resistor R41//R42. If the voltage across C27 increases above 39.7V, the voltage drop across R41//R42 will increase so triggering the comparator.

Am I right?

What's the purpose of C34 in parallel with R43 at the MOSFET gate?

About U6B: Why do they directly connect non-inverting and inverting inputs to ground and VCC respectively? Is this done for unused comparators?

Note: This circuit is powered using current from a CT if connected through Pin 1 of J18. That's why it bypasses diode D10.

Link to the App Note: http://www.ti.com.cn/cn/lit/ug/tidu224/tidu224.pdf


texts:
I am trying to design a driving board for a spectrometer, which requests 5V constant DC supply. Due to its sensitivity, I want to make sure about the voltage provided to the sensor. The supply is going to be provided from an embedded board (e.g., Beaglebone Blue). Is there any reason why I should add any regulation component(s)? Should I add a voltage regulator or a zener diode?
Thank you.

First, regarding the voltages provided, I could also have 3V3 available provided from the main board. Would it be better to provide 3V3 and add a boost converter to 5V or provide 5V and add a crowbar circuit? Which are the pros and cons of each solution?
Also, regarding the fuse at the start of the crowbar circuit (please refer to the image attached, which I have taken from the TL431 Texas Instruments datasheet), wouldn't it cause a voltage drop from the 5V provided? Is there another point of the crowbar circuit where I could place the fuse?


texts: Can FPC 0.5mm cause usb 3.0 interference inside itself?

texts: I am designing an 4-port USB 3.0 hub and using fpc 0.5mm connector to connect it to other usb devices. Will using fpc 0.5mm cable have interference because of high data rate? I am talking about the interference inside the cable itself from D+,D- to SSRX or SSTX wire. I have been reading and only found out that it cause interference to wireless devices but nothing about interference inside the wire.


texts: Can fire survival cables be used in underground tunnels for emergencies?

texts:
I would like to know where fire survival cables can be used
https://www.pyrosales.com.au/fire-survival-mi-cable - states a few including tunnels, shopping centres etc. Where are they mainly used and are they only ever installed for emergencies?


texts: Why do AC motors have various back EMF shapes?

texts:
I just saw in one of the threads that apparently, a permanent magnet synchronous motor and a brushless DC motor have different back EMF shapes. But why? I thought those two were exactly the same in construction, and there was only an integrated inverter upstream in the BLDC?

If those 2 are not the only ones to have various back EMF shapes, the bonus question is: what's the back EMF shape of the various AC motors technologies?


texts:
I am currently trying to make my own stm32 development board. i have stm32f100c4t6 microcontroller mounted on pcb.
   I am using Atollic True studio free edition. i had made small blink led program as below.

#include <stddef.h>
#include "stm32f10x.h"

void delay(int count)
{
    volatile int i;

    for (i = 0; i < count; i++)
    {
    }
}

GPIO_InitTypeDef GPIO_InitStructure;

int main(void)
{
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3 | GPIO_Pin_4 | GPIO_Pin_5 | GPIO_Pin_6 ;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    while (1)
    {
        delay(100000);
        GPIOA->BSRR = 0xF << 3;
        delay(100000);
        GPIOA->BRR = 0xF << 3;
    }
}

I have used st flash loader demonstrator under windows to load program to flash memory. however it detects the flash memory size as 32 KB whereas actually it has 16 KB. but program loaded to flash and verified successfully. (it detects device ID as 0x420 which is for medium density value line whereas this microcontroller is low-density value line.)

When i change the jumper setting of BOOT0 to ground to put it in execution mode, nothing happens. the pin PA3 to P6 remains at 0v.  i have connected 24 MHz crystal as main crytal and 32.768KHz as RTC crystal. I can get voltages around 1.8v at 24 MHz crystal. the other crystal pins remains at 0v. is this wrong?

I have also tried stm32flash under linux to load program, it loads and verify the program sucessfully. but, it also detects microcontroller as mediam density value line (128 KB).

I am stuck at this situation. any help would be appreciable.

Thanks for reading.

EDIT: I have attached link of
 schematic.


texts: Why MOSFET source is indicated with arrow ?

texts:
I know that , a basic MOSFET contains source and drain , and either it's a NMOS or PMOS ; it is indicated by an arrow at source . But let's look at a fabricated NMOS.

Here we can easily see that either a pin is source or drain is totally depended on the connection. Without connections , this device is symmetrical . But look at the conventional MOSFET symbols .

all these symbols marking a pin as source and other one as drain. Why is that ? Why this symbols are not symmetrical as the device is?

When I work on Cadence , schematics symbols all have this types of symbols where sources are marked .But when it will be used for fabrication , source and drain will be determined by the connection , not by the symbol.


texts: XC8 compiler: Same variable names across different C source files causes issues

texts:
I am currently working with a PIC18F25k80 device using the XC8 compiler and MPLABX.
I spent the whole of yesterday trying to debug some code I ported from a PIC32 micro project. This code did not interact with any hardware, and was split into 2 different source files.
Eventually, I was able to solve the issue by identifying that the XC8 compiler produces unexpected results when variables of the same name exist in different source files. NOTE: I did not use the "extern" keyword, as I needed the variables to be logically different across the source files.
I had to prefix all my my variables with a source file specific prefix.
Is this a known issue with the XC8 compilers?


texts: How do I sample a -2 V to +2 V analog signal with a PIC microcontroller?

texts: I am using a PIC micro with a 10bit ADC to take readings from an analog signal with a frequency less than 300 hz. However that analog signal is in the range of -2 V and +2 V. How can I condition the signal to get it into a usable range (assuming the input to the ADC has to be positive) Also I do not have a positive and negative power supply.


texts:
I have an old PSU which has an output of 18Amps at 12Volts DC. Is it dangerous if I touch the wires? Or is the voltage too low to jump my body (I heard anything below 40 Volts DC can't be felt by your skin).

I won't open the casing of the PSU so I won't come in contact with the charged capacitors.

I'll use the PSU to power a HHO generator


texts:
I will try to make the game MegaMind. I need to get a random number, but how can I get these?

I have tried something:

secret_code[1] = random()&=6;


texts:
I am trying to trigger a camera from another primary camera. The circuit diagram provided is as follows:

The signal to the input is suppose to be a positive square wave. So 0V..and a peak to peak of 3.3V. Instead, I am getting a DC offset of about 1V, and a peak of about 0.5V (max at 1.5V). What might I be doing wrong here?

I realize the camera wouldn't even trigger with a 460 ohm resistor, so i dropped it to a 200 ohm resistor, and it gives a somewhat erratic timing.


texts:
I am trying to generate a programmable Bias voltage from 0 to -2V with <0.5mV error.

I was able to generate a programmable positive bias voltage of similar range using DAC. based on this resource .

http://www.ianjohnston.com/index.php/onlineshop/handheld-precision-digital-voltage-source-detail

My idea is to have a negative 5 Voltage supply on the board and connect 0V to 5V, -5V to the ground, So everything is inverted, it will just give me the negative bias voltage with the same accuracy.

However, My problems is that The DAC requires SPI communication from uC which is 3.3 V.  I could not talk to the negative section of the board since They are at completely different voltage level.

Is there anyway for me to get around this?   Do i have to get another uC on the board just to talk to that DAC?


texts: I have been given a specification for an LVDT transducer where I was expecting a clear Va, Vb relationship. The Va and Vb are however described as having a phase and an non-linear relationship (i.e. Sin/Cosine ArcTan). Is this likely to be a resolver on a cam or some specially wound LVDT? (i.e are any LVDTs specially wound to produce an emulated resolver waveform?)


texts: Is a relay stressed by a partial activation of the trigger?

texts:
I'm using a relay like the one in the picture, controlled by an Arduino.
I basically use it for turning mechanically on/off a circuit, when i have 0 as constant output from a series of values that describe a sinewave.

The system does what i expect, but every time that the sinewave cross the 0, it gives an input to the relay.

The input is so short that it doesn't trigger its status... this is perfect for what i want, but i don't know if this stress applied to the relay might brake it in the long run.

right, i should be more precise...

the arduino is comunicating with the DAC of a circuit via SPI. No waves from Arduino itself... it just gives the values to the DAC which then generates the wave.

The entire system have not be designed to be switched on/off by software (i need to automatize the process and save the battery). So, for controlling mechanically the ON/OFF of the circuit i added the relay, connecting it with a digital pin of arduino.

In the arduino firmware i figured out how to turn the relay OFF when the values of the wave are equal to 0 (so there is not real output), this work very well.

The problem is that since the values describe a wave that goes between positive and negative values, the 0 is "touched" for each period of the wave.

Apparently this give no problems, because the relay doesn't turn the circuit off, but i see that one of the LED of the relay module blinks according to the frequency i set, and the relay makes some noise with a pitch that vary also according to the frequency.

The relay is placed between the circuit and a 9V battery, so no much current going on there, but I don't know if this stress might brake the relay.

Here an approximate schematic... if it can help...


texts: Since a bipolar junction transistor (BJT) in a common emitter (CE) configuration is not a linear device, the varying voltage signal will not produce a current of the same waveform as at the base, and hence the output voltage waveform is not going to be a multiplied version of the input voltage signal. What does that mean? If I want an amplified signal at the output must I use a current signal, not a voltage signal?


texts:
In a recent lecture in my AC Circuits course, the professor put this slide up and hastily explained the Universal Op-Amp. Since I already struggle with circuits, let alone operational amplifiers, I did not understand his explanation very well. What is Ag, Rg, or Ai?
Could someone with extensive knowledge on Op-Amps break this slide down for me so I can have something to complement the lecture I received?
Also, what is the purpose of these types of Op-Amps?
They look very similar to summing Op-Amps. Also where it says, "This formula subsumes all previous configurations," the professor had just gone over five standard Op-Amp Configurations prior to this one.


texts: Why is oscilloscope measuring a higher voltage at high impedance?

texts: The input to the scope is 358 MHz sine wave. It's coming from a four way power splitter, unsure of what is upstream of that. At 50 ohms its measuring 931 mV peak to peak. At 1Mohm its measuring 1.27V. Is the higher voltage measurement a result of the impedance mismatch at 1 Mohm?


texts: Measuring wow and flutter of a phonographic turntable with digital equipment

texts:
The old school way to measure: 3000 or 3150 kHz test tone from test record played back through phono cartridge/preamp into wow/flutter/drift meter and for turntable that has an electronic adjustment to optimize wow and flutter/rotational speed stability, adjust for minimum needle deflection on analog meters.
With DSOs and FFT analysers is there a more accurate way?


texts: Why do digital scopes sample signals at a higher frequency than required by the sampling theorem?

texts:
In the quest for a not so expensive PC scope/logic analyzer, I have found a nice little device it looks very well done and I know it will do the job.

However looking at the specifications, I encountered this:

  Bandwidth vs Sample Rate

  In order to accurately record a signal, the
  sample rate must be sufficiently higher in order to preserve the
  information in the signal, as detailed in the Nyquist–Shannon sampling
  theorem. Digital signals must be sampled at least four times faster
  than the highest frequency component in the signal. Analog signals
  need to be sampled ten times faster than the fastest frequency
  component in the signal.

And consequently it has a sampling rate of 500MSPs but a bandwidth(filter) of 100MHz so a ratio 1:5 for digital signals and a sampling rate of 50MSPs and a bandwith(filter) of 5MHz so a ratio 1:10 for analog signals

As far as I understand Niquist-Shannon only talks about sampling at twice the maximum frequency (in theory), It is of course good not to push the limits and there are no perfect filters. but even a simple UART samples a digital signal at the same speed than the baudrate!

So is this a usual rule of thumb for sampling? or is this something someone from sales may have written? It lets me somehow clueless I have never heard about this.


texts: I have several projects that designed by a different designer .They used personal library with specific Item ID for the same component. I want to manage them and link them to a supplier. If I do that one by one, it takes a long time. Is there any way to change them or apply changes on all of them in short way?


texts: Transforming bike dynamo output to reduce diode bridge loss ratio

texts:
I'd like to use a standard 6v/3w bike bottle dynamo to power a 18650 battery charging module TP4056 which also powers some LED's.
Diode bridge rectifier steals 1.4v from the generator. In addition to reduced output voltage, a large portion of period would be without any current (all the time while absolute value of voltage is under 1.4v).
So, could I reduce this inconvenience by attaching a transformer right after generator, to multiply voltage by 4 and attaching output of the transformer to the diode bridge and on to the battery charger?
Would the transformer losses be smaller than the loss of having to use only diode bridge?
Which kind of transformer would fit this purpose?


texts: Theory question about "j" imaginary unit (AC circuit analysis)

texts:
I have just started to learn about AC network analysis and have some questions about "j" (or "i" on my calculator), the imaginary unit.  My book doesn't go into a great deal about this, and jumps right into formulas and substitutions (more practical approach, not theoretical).  So, what exactly does J represent?

I see that if I draw a complex-plane (y-axis being imaginary, x-axis being real), and draw a unit circle on it, a 90° angle is \$\sqrt{-1}\$, which is "j".  I see that I can use this substitution in phasor form when, say, solving for the voltage across a capacitor when the current through it is known:

$$V = \frac{I}{j \omega C}$$

Can someone help me understand this?

To be honest, this question is pretty vague because I'm not even sure how to ask about what J is; it's that foreign to me.  I would like a common-sense explanation (big-picture) of it's meaning and purpose in AC circuit analysis.  I'm not necessarily looking for a rigorous mathematical explanation (although any necessary mathematical explanation is welcome).