texts: DC voltage controlled current source circuit for high currents

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I need to make a voltage controlled current source for nichrome wire as part of an experiment. It seems like I need a circuit which can translate a microcontroller's  0...5V range voltage to a 0...8A current. I mean a voltage controlled current source. I can use a DC power supply which can supply this current.

Is there a topology or any suggestion circuit for example composed of an opamp and a power transistor? Or any specific IC would work as well.

I would be glad if one can share a circuit diagram for this purpose. (An opmap followed by a power transistor was in my mind but Im not expert in the topic)

MAJOR EDIT:

I think PWM control is better for power consumption. So the uC's PWM pin is the input signal. Here is what I have in mind so far. But never tried such high current circuit before:

And here is simulation results for current, instantaneous power and average power:

Some more info:

PWM will be 490Hz frequency.

I'm planning to use this power MOSFET.

Flyback diode is a 1N4007.

I would be glad to hear about any suggestions such as the MOSFET ratings, heatsink required or not or any circuitwise mistakes here.

EDIT 2

Here is the new circuit with a MOSFET with a lower Rds(ON):

I had to modify Rg because it wasnt saturating the new MOSFET sharp enough. I reduced it from 10k to 220 Ohm. And R_col was too low for a quarter watt resistor. I can only make comments on it by looking at the simulation below:


texts:
I am trying to measure the output power for BLDC controller, in order to calculate the efficiency of the controller. I came to know that two watt-meter method is one of the method used to calculate the three phase AC power.

But instead of using two wattmeters, i have.....

Two clamp meters (AC/DC clamp meter) for measuring Ir and IY.

Two multimeters (AC/DC) for measuring VRB and VYB.

My input power is DC 48 volt. P = V × I will give me the input power.

But to calculate the output power has complexity.

W1 = IR × VRB  and  W2 = IY × VYB
W1 + W2 gives the output power.
For voltage measurement VRB and VYB:
My bldc controller output is trapezoidal waveform with variable output frequency, Vrb and Vyb can be calculated by using ac multi meter. Because ac voltage does not depends on the Frequency, whatever the Output frequency the Vrms will be the same i guess. Correct me friends if i am wrong.
For current measurement Ir and Iy :
Since the AC current must not be same for different frequency at all time. How to calculate the AC current at my output frequency say (eg: 100 Hz).
Edited...
Sorry i forgot to say something, I am driving the bldc controller with bldc motor in a load setup.


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I have a project that uses 12S LiFePo4 batteries, and I need an electronic speed controller. The main problem I have is that pretty much all the existing ones I've found are designed to work with Li-poly batteries.

I've seen this post: Will LiFePo4 work with ESC for LiPo?

But the concern I have is that will Li-poly ESC's actually work for LiFePo4's when you consider that they have different cutoff voltage's.

Li-poly has shouldn't be discharged at anything less than 3.0V, where as LiFe's should go to 2.8V and that's a major bottleneck considering that they have a nominal voltage of 3.3-3.2V.

If someone could point out to me how I can make this work, or if I'm wrong / recommend an ESC, etc. It would be greatly appreciated.

Any answer helps!


texts: Is this an accurate model of a microcontroller pin?

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For something so common, I can't seem to find anything online on what a microcontroller pin "looks like" (besides a high-level voltage source when output, open-circuit when input). So I decided to just do it myself - let me know what you think. Obviousy specs as per transistor characterstics, pull-up value, etc. aren't important for this.

Functionality:

State (Input or Output):

When 0V, input (just like code), Q1 is off and output voltage is disconnected
When 3.3V, output (just like code), Q1 is on and output voltage is connected to the pin

Output:

When 0V, low, outputs 0 volts (duh)
When 3.3V, high, outputs 3.3 volts (duh)
Only makes it to the pin if state is high

Input:

High-Input impedance straight into gate
If 0V, Q4 is off and so "input" port will read 0V or low
If 3.3V, Q4 is on and so "input" port will read 3.3V or high

Pull-Up / Pull-Down

If they are 3.3V, connects the pin to a pull-up or pull-down resistor.
If they are 0V, FET is off and so the resistor is floating there not affecting the circuit

Thoughts? In terms of anything maybe missing / unnecessary. The state and pull-up N-Fets probably aren't necessary - they are just there to make the logic not inverted and the system easier to understand.


texts: Altium: Find schematics which use a footprint from the library

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If I search for an item, and I find it's footprint, can I find which schematic/part it was referenced to. E.g. finding corresponding wiring/schematic symbol?

Thanks in advance for your help.


texts: can anyone explain 2nd quadrant operation of DC chopper in easy way? may i  ask about  how brake applied in 2nd quadrant


texts: What is the advantage/Disadvantage of Lap Progressive and Retrogressive Winding?

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Picture source.
I would like to know what is the advantage/disadvantage of the two windings. Their different I could understand. I searched over the net but I could not get. I got the advantage/disadvantage between lap and wave winding only, where these two progressive and retrogressive are lap windings. What is their advantage/disadvantage? Which one is better? I saw some small motors could be progressive while some other could be retrogressive, nothing specific.


texts: How to prevent sealed in product battery drain on store shelf?

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How can a microcontroller-based device prevent battery drain while the product is on the store shelf? We are creating a waterproof, sealed in product without any buttons. This means the battery is attached to the PCB in production and can't be accessed after production.

What I'm looking for is a way to prevent battery drain while the product is still in the box and on the shelf.

Here's what we've doing so far and why I don't like it:

We're using a normally closed magnetic (reed) proximity sensor on the board and a permanent magnet in the box. The magnet breaks the circuit and no power is applied from the battery to the circuit. Take the product out of the box and it should automatically go live.

What I don't like:
Normally closed reed switches are scarce and expensive. They are also often too big for our small product. On top of that, the ones we've been using have very fragile SMD "legs" that break from their solder pads at the slightest impact.

Edit: We have two GPIO pins accessible on the outside of the product and would be replacing the reed switch inside the product.


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There is a type of bulb in the market nowadays that detects load-shedding! I mean it keeps lighting after load-shedding. But my curiosity is if I turn off the switch of the bulb, it might have detected that load-shedding has occurred, but it doesn't! How does exactly it detects electricity outage!
I want to know the electrical working behind it.

[EDITED]

Here is a video of that product (not exactly mine, but similar)
https://www.youtube.com/watch?v=T9yfgc3FpW8

I'm from Bangladesh, yep here load-shedding means turning off in a grid for a short period of time.

My Building has no special electrical connection.


texts: Is a cascode better current source than current mirror ? Which option is better?

texts: I have simulated a cascode and made a M2 in saturation so it will act as a current source. I want to understand which current source is better. Is cascode better because it has a higher output impedance than the current mirror ?


texts: Some pointers on how to begin VHDL writing

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I'm currently doing some tutorials and reading some books on how to write VHDL. As I'm curious and learn better with hands-on tutorials I'm going to start implementing my projects that will serve me well in the future.

For my first real project I'm trying to implement an arctg function followed by an aggregation operator function.

I don't want to reinvent the wheel and I don't want to be further confused and so I'm asking here the following questions:

The integer to float and vice-versa with the bits of the mantissa, exponent and integer is necessary right? Isn't there any website where people have already implemented this kind of things and share with the community?
I've seen  somewhere that the package math_real already has an ARCTANfunction which accepts a REAL which I guess is a float. So:

2.1. Is this synthesizable? If not why is it even coded?

2.2. If everything needs to be converted from float to integer in order to be passed between functions, why does ARCTAN accept REAL and not an integer?


texts: Detect power supply voltage threshold, while consuming very low current

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Lead acid batteries get damaged by over-discharge somewhat like lithium polymer batteries.
I need a circuit that will cut off the load from the battery when it drops below about 10v. That is the easy part.
The hard part is having a circuit that consumes a miniscule current and wait until the battery's voltage exceeds around 13v, (which would indicate that it is being charged,) at which point it would re-engage the load.
The best idea I have is to use a low-quiescent current voltage regulator, specifically the TS2950CT50 +5v which has a quiescent current of around 75uA. I would use a mid-range PIC16F MCU that has an internal voltage reference (and either ADC or comparator) that goes into standby mode, periodically checking if the voltage exceeds 13.5v. The MCU could consume as little as a couple of uA.
While 75uA isn't too bad, I was wondering how I could achieve a lower standby current.
Another idea which I'm not certain about at all, is operating a zener diode below its breakdown voltage, relying on a slight increase of leakage current to trigger a MOSFET circuit. Leakage for zener diodes seem to be 1uA per volt, so that would in theory only consume 10uA. But since zeners don't have a great accuracy at the best of times, let alone over different temperatures, with aging, EMI or what have you, could I use this reliably?
At a push, it would be permissible to have the over-discharge protection deactivate when the battery's voltage reaches anywhere between 12.5 and 13.5v.
Because I'm a masochist, I'd prefer not to use an IC which is dedicated to this purpose (not that I've found one). What other solutions are there?
Thanks


texts: 9 Pin D Plug Cable Assembly: Fitting more than one thing into a solder bucket

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I want to terminate a cable in a 9-pin D plug. The design I’m working on needs a resistor and two capacitors at the terminals of the D plug.

I can’t work out how to successfully work Pin 7 – I need to join together the resistor, a capacitor and a wire to Pin 2. The thinnest wire I have is 24 gauge, 0.511 mm, and the diameter of the solder pots is 1.5mm. Diagram 1 below shows the plug wiring

My plan is to join the wire, R1 and C2 together using a lash splice.

This is proving really hard to do in practice. Only one wire can fit into the solder pot; the other two have to be joined 3mm above the tip of the wire going into the solder pot.

So - is there a better way to do it?


texts: What is an analog multiplexer? Do we have a 2:1 analog mux?

texts: I have two analog signals with frequencies up to 8kHz. I need to select one of the signals using a digital logic select. How can I do this? I need the most reliable IC as our system demands the highest reliability.


texts: Is it better to run a 24V tec on 12V supply if no controller is available?

texts: I’ve built a prototype cooler using tec modules to liquid cool a human body powered from a 12-14v supply with 30A maximum, using 4 x 70W 12V modules. It works fairly well but looking at the graphs for efficiency I wonder now if using 24v modules powered from the same supply would do?


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I want to build a USB Programmer currently for AT89C51. I am stuck on how to make it communicate with PC. In RS232, the RxD TxD pins are straight forward, we just need to use Logic Level Converter to interface with MC. What about USB. Are Data+ Data- lines equal to RxD TxD? Can I connect these USB Data lines to MC directly? They don't need any Logic Level Converters. Right?

I saw some USB to RS232 converters. Why they exist?
I thought USB interfacing was more easy, not really!

So how would i send data from PC to my Programmer through USB port?
Please Help & Thank you


texts: Calculate spherical surface area of IR emitter

texts:
I have an IR LED emitter.
It has a 20 deg. beam width.
The total power radiated is 70 mW.
I want to calculate the power density (mW/cm^2) at a range of 30 cm.
How do I calculate exactly, the area of a sphere that is intercepted by the IR
beam at 30 cm?

I have done an approximate calculation by assuming that the radiation is a cone,
and I have calculated the area of the base of that cone, but this is approximate and I would like to calculate the exact surface area of the sphere, intercepted by the beam.

I did find one post of a similar problem, but the person who kindly answered the post simply gave the resulting number and did not mention the formulas he used.

If I have posted in the wrong forum, would you kindly tell me which is correct forum?

Thank you.


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I'm building this circuit:

I'll be use a 12v DC power supply (same as pictured), but with a 220uF electrolytic capacitor because of the 400 ohm 12v relay I'll be using (instead of 220 ohm).

But looking through the toggle switches available, there are tons. I guess I need a SPST, or a SPDT wired to act like one? Also, it should be On-On?

My main question is on the ampere rating required. Would a 3A switch do? How can I calculate the amps required?

I tried Googling, but can't find any info. More info on the circuit itself is in my other questions.


texts:
Currently I'm doing a project where I am simply trying to get a robot to move forward without code by using say a push button or a potentiometer. I plan on moving on to micro controller later, but right now I'm trying to work with my first perfboards and soldering irons. It has 4 DC motors, each with a free current of about .4A and a stall of 5A, but I don't really know how to hookup the circuit correctly. Each motor uses about 7 volts. I was wondering
a.) Is there any specific way I should construct motor
b.) What type of battery should I use to power the circuit saftely


texts: Sketch a Bode Plot for the Loop Gain of the circuit

texts: Below I have the transfer function, but I am still uncertain about Bode plots. How do I know the slope, how do I know where the zeros of the function are?


texts: Number of bits for tag, index, and block in a direct-mapped cache

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Suppose you have a 64-byte cache on a system with 16-bit memory addresses.  If the cache is direct-mapped and it has 10 bytes of tag overhead in total, how many bits are used for the tag, index, and block offset within the 16-bit memory address?

I found this in the textbook Computer Organization and Design by Patterson and Hennessy, and I was hoping someone could work through it for me.  In particular, I'm curious as to what "10 bytes of tag overhead" is and how it effects what the solution is.  How are the tag, index, and block offset generally found given some cache design?


texts: Why doesn't current flow through the common part of a circuit?

texts:
I'm reading a book on computing that has a couple of introductory chapters on electronics. The author imagines a situation in which you and your next door neighbor set up a bidirectional telegraph to communicate with each other at night via Morse code:

And then you and your neighbor realize that a common part of the circuit can be shared to reduce wire costs:

Where I get confused is how the author analyzes the circuit when one or both switches are closed. The author depicts the closing of the switch at battery 1 like so:

He says that no  electricity flows in the other part of the circuit because there’s no place for the electrons to go to complete a circuit. My question is, why can't electrons also flow from the negative terminal in battery 2, through the right bulb, and into the positive terminal of battery 1?

He also analyzes the situation when both switches are closed:

The author states (with absolutely no explanation) that "No current flows through the common part of the circuit." OK, but why? Why doesn't current flow form the negative terminal of battery 1, through the right bulb, and into the positive terminal of battery 1. And why doesn't current flow form the negative terminal of battery 2, through the left bulb, and back to the positive terminal of battery 2?


texts:
I have a question what exactly does a MEMS piezoelectric sensor chip contain. Does it contain the sensor element alone (or) also the signal conditioning circuitry for the MEMS piezoelectric sensor as a microelectronic integrated circuit (nanometer/micrometer level).

From what I understand, MEMS sensor has capacitor fringing plates with a seismic mass and then the changing capacitance between the plates is proportional to the acceleration.

I guess the signal conditioning circuitry would be on the chip due to the proximity.

Also, is it possible to process the signal off-chip as well?


texts: I have made a CPU on an FPGA board. It works great but I cannot proceed to make a computer with it until I have an input. What use is a computer if it can talk to you, but you cannot talk to it? It runs all on 5V, has essentially a 20 bit address line, is 8-bit, and essentially operates at 12.5MHz. I may speed it up later, so what I am looking for is a maximum of 3 chip solution to give me keyboard input via PS2 or USB. It must give parallel output and operate within 55ns(as I may speed it up). An Atmega is not fast enough.


texts: Confusion with calculating the mantissa of a floating point from a binary number

texts:
I use this converter to convert a 32-bit binary number to a floating point number. I first find the hexadecimal of the 32-bit binary number and convert to decimal by using the converter.

In my case the 32-bit binary number is: 11001010110010001101011010011001

This is CAC8D699 in hexadecimal.

Below shows this example conversion:

The result is -6581068.5.

I can understand how the sign and the exponent is calculated. But I tried to learn how the mantissa is calculated and could not find a clear explanation.

How is the 23-bit mantissa section i.e. 00110001110001110111000 converted to 1.5690490 in this case?


texts: In Circuit What is R ,Y ,B written in box?

texts:
sir,
I will make a automatic single phase changer. and I found a circuit on a net.
I have a doubt related to circuit.

1 ) according to this circuit we need a step down a phase.

2)  what is a R,Y,B in box.


texts: can anybody help with troubleshooting steps for this 3phase generator? not sure which AVR it needs, so i would like to check the stator and coil is ok first.


texts: Motor controlled with a solid state relay not starting

texts:
We have a solid state relay controlled by a Raspberry Pi, The relay is interposed o the negative wire between a 11-12V battery and a motor.

If I measure the voltage before entering the relay, it is correct. If I measure it on the output side I get 0.44V and the motor won't start.
However, while the Relay is ON if I interrupt the negative wire and I connect it back, the motor works(While the relay is still on).

I'm not sure if it counts, but I use a LiPo battery.

What is it happening? How can I solve this?

Edit: This is the SSR that I use: https://www.aliexpress.com/item/2-Kanal-OMRON-SSR-Relais-G3MB-202P-5V-DC-2-Channel-Solid-State-Relay-Board-module/32830801262.html?spm=a2g0s.9042311.0.0.27424c4d4M3JQz

And its datasheet: https://www.openhacks.com/uploadsproductos/g3mb-ssr-datasheet.pdf


texts: Can I use a 3 pin kettle power lead instead of a 2 pin kettle power lead

texts: I have a computer appliance that only accepts a 2-pin kettle power cord (UK plug type). I don't have a 2-pin available at the moment; only a 3-pin. The third pin that is missing is the ground connection. Would it be ok for me to use the 3-pin kettle? Both are 10 Amp, 240 V cables.


texts: Can 12V relay be used instead of 5V relays?

texts:
I have the project of making a touch switch using the IRFZ44N MOSFET for making a small led glow and stop glowing when I touch the probes. I thought of using a relay if I have to make a bulb glow, by connecting to the plug directly. I searched on the internet and found that most projects used 5V relays. But is it a problem if I use a 12V relay, instead of a 5V relay?

(Please don't mind if the question sounds silly, I am new to electronics and electrical)


texts: Can anybody explain the heat produced in the circuit during operating and non-operating state

texts:
I have designed motor monitoring circuit(Agricultural Purpose) with Stepdown transformer, Rectifier, Relay Module, and processor.I planned to run the module to run 24*7 but I afride that heat will affect the circuit.My circuit working is When the relay module triggered the circuit got closed and the processor will handle remaining work.

Here my Question is if the relay is in Off state(load is connected to NO, No load connected in NC) still my transformer and rectifier circuit get connected to the power supply which will produce heat or it will not produce heat?


texts:
I was learning about power mosfet and i decided to try some switching circuits in multisim, so i chose a random n-channel Power mosfet and set up this circuit

when 10V is connected to the gate 15 A flows and there is no problem, but when ground is connected, 2 A flows, i didn't know what's wrong so i tried again using IRFP351 ( and decreased 350 to 340 V) , which is ( according to the datasheet) the same but lower voltage rating ( 350 instead of 400) and it worked fine.
So i have no idea what's the problem???, i am pretty sure it's not the setup because i used the same with IRFP351. Is there something about ratings i dont understand?


texts:
This is sentence from Design of Analog CMOS Integrated Circuit that I don't understand.

  Note that the current source injects current into ground or draw current from VDD. In other words, only one terminal of each current source is "floating".

Does this mean that, for a MOSFET to be used as a current source, the source of an NMOS should be connected to ground and the source of an PMOS should be connected to VDD?
No other cases are possible?
I mean for example for NMOS, the source may be connected to something else than to ground.


texts: Making a high speed USB communication from STM32F4 and Java on Linux PC

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I have a STM32F4Discovery board and I try to communicate between a c program(with no OS)on the board and a Java program on ubuntu pc. I have found many tutorials like this about USB but they all try to make a RS232 like serial port which is too slow(like 9600 baud or max 14.4Kbps).

Right now I am lost and I need to find out what how should I make this. Is it possible to make a high speed communication in this case and how fast it could be? USB 2.0 specs says it could be up to 480Mbps. Could you tell me with which library is this possible? And is there any best practice available to follow for making a two way communication over USB?

I really appreciate any hints.


texts: Is it OK to put traces under castellated PCB

texts:
If we would speak in general: what is the strength of the solder mask in terms of breaking voltage?

So if we put one PCB with castellated pads on another board like this:

What will heppen if both PCBs would have traces one on another (meaning bottom layer of the top PCB and top layer of base PCB)?

I'd say that it should be OK for low voltage schematics. But what if the voltage is 230 VAC?


texts:
Some I²C devices like the MCP4728 DAC have a small EEPROM allow programming the I²C address (and other configuration bits).  I know that in high volume can be programmed by the vendor, but for low volume prototyping, how are these typically programmed?

Are they programmed on the board?  If so, how can you configure just one component if there are more than one on the bus that need to be configured and they all come with the same address?
Do they need programmed one at a time with all others powered off?
Other best practice suggestions would be appreciated!


texts: What are these two components on my PCB from a PIR?

texts:
I'm new to electronics, I understand most of this PCB, but the two marked components are a mistery to me, and I can't find their names.

The blue one is some kind of switch for the LED, as you can see from the top view. But when i cap it it just keeps the LED always on, and not only when the sensor activates (the sensor had this functionality before).

The red one I have no clue what it is, or what it does, it just says TAMP on the side.

Any clues? I have little to no idea what I'm doing.


texts:
I've got a devices that is really strange, it drops USB periodically. By periodically I mean on a weekly (or biweekly) basis. By dropping out I mean windows loses the handle to the driver. Dropouts a not tolerated well by those using the devices. The weird thing is I use a similar design on most of the products that we have (more on that later), for some reason this one doesn't want to play nicely, some of the other devices run for months to years (with the same design but different layout) with zero issues.

It's only on some of the devices so that probably rules out firmware/software.

The USB is 2.0 FS, running to an STM32, with an ESD diode chip in the middle.

Schematic (D+ and D- and OSC_IN and OSC_OUT (oscillator design was inherited) go to their corresponding pins)

A better question would be, how do I test for these dropouts? Is there some method that could monitor a device for very long periods of time with millions of packets going by and find the source of the error?


texts:
I am trying to size a circuit breaker for a transformer.

The transformer is three phase 480 : 4160 V rated at 25 kVA. From my calculations there will be approximately 30 A on the primary and 3.5 A on the secondary winding.

Do the circuit breakers have to be voltage rated? Since the secondary winding is a medium voltage does that affect the type of breaker used?

I have found information on the NEC guidelines but I see that this is for the US is there any equivalent for the UK?

Will I need a circuit breaker for both the primary and the secondary winding?

Any help with this matter would be much appreciated.

Kind regards


texts: Can anyone pls troubleshoot this circuit?

texts:
I know probably there is a silly mistake in my circuit, but I can't seem to find it !

The circuit is a non inverting amplifier supposed to amplify the input signal (which has a range of 0 to 5V) with a gain of 2. The circuit needs to work off of a single supply of 12V. Is the schematic correct for these specifications ?

Also will the circuit output 0V when the input voltage is 0V(or will the voltage be the lower saturtion voltage of the IC)?. By the way, I have to use this IC, hence I cannot use a rail to rail op-amp.


texts: Parallel resistor and capacitor in non-inverting voltage follower

texts:
For an inverting voltage follower, C1 would be part of an LP filter. But in the depicted non-inverting voltage follower circuit, what is the purpose of C1 (if any)?

simulate this circuit – Schematic created using CircuitLab


texts: How to calculate if flyback diode needs heatsink?

texts:
I'm designing a circuit for automotive use, where I control various kinds of inductive loads (motors, solenoids, etc) up to 20A (Máx). In the design i'm looking into using 2 SMD N channel MOSFET in parallel (Vishay-Siliconix/SQJ142EP-T1_GE3) to control these loads with a 100Hz PWM signal and in parallalel with the load i'm using a SMD flyback diode to reduce voltage spikes (STMicroelectronics/FERD20H100SB-TR).
Since I'm only using SMD components i did not want to use any kind of heatsinks to save space in the PCB, but i'm  having problems to find out if this diode will need one. How would I calculate that that?
P.S. The ambient temperature this PCB will be subject will be about 65°C - 70°C (149°F - 158°F).
P.S.S. Here is a picture of my design schematics  (Schematic)


texts: How to calculate this LDO regulator, and how to prevent it from oscillating?

texts:
I am further playing around this PMOS LDO circuit I designed and attempted to test and rate (the Edit 3 schematic, simplified by removing the protection circuit). After I dropped in a NJM4559 op amp in place of LM358 it started oscillating (previous record was none of LM324, LM358, TL084 or OPA2134 oscillated). Is this a blessing from TI? (kidding)

How to calculate this circuit, since I have one more MOSFET than what I found in TI's application notes. If it was oscillating, how to stop it from doing it?

My way of determining whether the circuit is oscillating is checking for the Moire pattern on DMM readings since it is difficult to have the LDO oscillate at the frequency (or a harmonic) of the DMM's internal clock frequency. Is this way of checking for oscillations reliable? Don't yell at me about oscilloscopes as I don't have one to start with. Donations are welcome.

Here I replicate the circuit I tested. The op amp can be any one of the following: LM324, LM358, TL084, OPA2134 or NJM4559, and the last of which oscillated. R6 is a load resistor I attach when testing and value options are 10 ohms and 1 kiloohm. Respect the part numbers as those are exactly what I used.

simulate this circuit – Schematic created using CircuitLab


texts: Supply a DC motor with a SMPS power supply

texts:
I want to supply power to a motor from a SMPS power supply. But the problem is SMPS supply have a feedback loop and a fail-back mechanism, so on the startup motor shows a near zero resistance [according to the electrical model of the DC motor ].

I don't have privileges to open up the SMPS unit and bypass that mechanism. So I need to find a walk around on this. Any idea guys?

I know motor soft starter unit will work, but I don't have that luxury to afford a one. Any other quick and dirty trick to make this work?


texts: What is the derivation for Shannon Hartley theorem?

texts: I know by Hartley's theorem that information is proportional to bandwidth and time. The capacity corresponds to information and bandwidth is there. I don't get how the logarithmic part corresponds to time. Is there a derivation?


texts:
In a few months I should begin developing a power converter and I was told I should get used to dsPIC. The currently used model is "dsPIC30F6010" which is kind of "old" (compared to the newer dsPIC33E/F series at least).

I saw the quite cheap (~ 35$ on Digikey) "DM330013-2-ND" development board with integrated debugger supporting dsPIC33F (as well as PIC24F/H and PIC32), though I seem to have more difficulties finding a cheap one for dsPIC30. I don't know if there are many differences between the two from a code style/functionality point of view.

I don't know what other people do, but I thought it would've been a good idea to start using PICKIT3 directly instead of using the on-board debugger since I'll have to make my own PCB. This somewhat narrows down the possibilities.

For the dsPIC30F6010 Microchip suggests the "DM183021" but it's very expensive (~ 130$ on Digikey). Another suggested development board is the "DM300019-ND" (~ 80$ on Digikey) which may still be within reach of my wallet, though I'd have to buy an add-on "MA300013" (which is obsolete ...).

If PIC32 and dsPIC30F/dsPIC33F are (very) similar from a code style/functionality point of view I may use a PIC32 board with the PICKIT 3 debugger, just to get the feeling of it.
Still, I couldn't find a good&cheap development board claiming to support PICKIT 3 programming or at least providing a header for it.

Does anyone know/use such a cheap (< 80$ if possible) development board?
I don't really need many advanced features (such as Ethernet, CAN, ...), though I'd like to have I2C/SPI/ADC/GPIO on board.


texts:
http://www.mouser.com/ds/2/395/DTA124%20EE%20A12-248319.pdf

It says it is a PNP transistor but symbol is of NPN transistor. The equivalent circuit shows the transistor sitting between load and ground which is how NPN is typically used.


texts:
Hey guys I am looking for a circuit where I can convert 100mV AC to 1V DC and then feed it to my microcontroller's ADC pin. Can any one suggest any circuit to achieve this?

I want to interface a split core current transformer (CT sensor) to my microcontroller and its rating is for 0-30A so it will give me an output of 0-1V AC. So usually I will get 100mV AC as my CT sensor output. I don't want a constant 1V DC. I just want to convert AC to DC so that I can give that as an input to the microcontroller and convert that DC voltage to some numerical values. For a microcontroller giving AC voltage to an ADC pin is not advisable right?


texts: What programmable switch to use on a 220 Volts AC load?

texts:
I'm building a circuit using PIC IC, to control the switching of a 220 Volts AC load. My idea is that the switch keeps supplying power indefinitely to the load when PIC is giving the switch an active low signal, and stops the power when PIC gives it an active high signal, and the power should remain OFF until the PIC is manually reset.
What switch would best serve my purpose? I'd prefer a simpler option.

Thanks in advance


texts: Could a graphene battery / supercapacitor be used to power a railgun?

texts: new to this StackExchange, but I have a question about graphene batteries / supercapacitor. From my understanding, graphene batteries / supercapacitors (not sure of the difference?) are superior to regular acid-based batteries because they can hold much more energy and also charge and discharge very quickly. I have read that the one of the biggest roadblocks to creating an effective railgun is the lack of quick discharge capability of normal capacitors. Would using graphene materials potentially solve this issue, allowing a railgun to be built in a much smaller (possibly handheld?) package? Really, I'm just looking for information about how graphene could potentially impact the design and capabilities of railguns. Thanks all!


texts: Electronic Circuit to Voltage control pan of stereo audio? (Modular Synth)

texts:
I'm considering making a Modular Synth module which would pan and modulate a stereo signal. So an electronic circuit to pan the audio from right to left, even allow audio signals crossing over, Left to Right, and back. Given it's for a Modular synth module it'd be Voltage controlled.

I'm not even sure where to start. It might be easier to just go digital and have a micro-controller control things. Analog I'd imagine I need to create two copies of Left and Right signal inputs, so you'd have Left_A and Left_B, and similarly for the Right signal. Those four signals would be amplitude modulated and then summed together again to the Output.

So LeftOutput = (? * Left_A) Plus (? * Right_A)
and RightOutput = (? * Left_B) Plus (? * Right_B)

I guess I need four voltage controlled amplifier/attenuator circuits and a two adders.

I'm not an electronics expert so is that possible, sane, the easiest solution?


texts: Opto-coupler to convert current into voltage

texts:
I am using TPS26601 for my next design. There is a pin IMON which outputs current proportional to current flowing throwing the output pin. The gain ranges from 72 to 85 µA/A (Page 7).

In reference schematics (Page 27), they have used a resistor at the IMON pin to convert current to voltage so that it can be sampled by an ADC downstream.

However, I am planning to use an optocoupler. The current that would be drawn from OUT pin of the IC ranges from 0.1 A to 2 A (or even more in case of short-circuit). So, the current that would appear from IMON pin  ranges from 8.5 µA to 170 µA.

I am not sure about optocouplers which can transfer signal if If ranges from 8.5 µA to 170 µA. For example, I was considering EL3H7(B)(TA)-VG and found out they don't show graph of Current Transfer Ratio in the range from 8.5 µA to 170 µA.

Is there any optocoupler which can be activated with the current in µA ranges?


texts: To find theRMS noise voltage in a circuit, can the measured RMS voltage be subtracted from the RMS voltage of shorted probes?

texts:
I'm trying to estimate the SNR of a circuit, which includes measuring the noise power of an analog trace. Right now, I'm attempting to measure the noise with a high bandwidth scope probe, ac coupled, low inductance ground leads, with 1x attenuation. However, I want to attempt to remove the RMS noise induced from the probe itself.

tldr: Is it possible to subtract the RMS noise measured with a shorted scope probe from the RMS noise measured of an analog circuit trace for a more accurate measurement of the actual RMS noise on the trace?


texts:
This is a LED driver IC. It says it can deliver 20V output, but what does that mean? That the output pin will have 20V in respect to GND? I am asking, because the max supply voltage is 7V, so does it have an amplifier inside?

Link to datasheet: http://www.farnell.com/datasheets/1837098.pdf?_ga=2.60289641.55768663.1518169214-1262566742.1517153785


texts: power supply for electrophoresis [100 V from 230V mains]

texts:
i am trying to make a power supply for electrophoresis, which requires 100V DC. The project is a funded non-profit for some schools, where there are strict requirements when it comes to the individual price.

One way to make the power supply is as posted in this instructable, where they use a boost converter from a 15v DC supply: http://www.instructables.com/id/Gel-electrophoresis-power-supply/. I have found that this in components will cost about 10$ plus the power supply.

Another way, would be to use the mains directly with a bridge rectifier trough a series resistor to a zener diode with breakdown of 100 volt. I know that it should supply between 200mA and 350mA of current when it is connected.

simulate this circuit – Schematic created using CircuitLab

The top circuit is the one i have tried and the only problem is that the resistor has to dissipate quite a lot of heat. But is has been tested to work.

The bottom circuit is one i found somewhere, which has next to no power dissipation, except for in the load.

The question stands, is there a better way to do it or is the proposed circuit safe. And will the alternative circuit work when you put 230V RMS on it? The circuit was found for lower voltages around 12V, so can i find a transistor that can handle my specs? The benefit of the zener versions is that they can be connected directly to the mains and doesn't need a separate dc power supply, which saves money.


texts: Merge a differential pair into one signal

texts:
I have an LVDS ADC connecting to an Altera Cyclone IV FPGA. The data pins come in 7 differential pair channels, for a total of 14 pins.

Although each differential pair is physically 2 pins, my Verilog code expects only one signal for each pair.

How should I tell the FPGA that each differential pair should be merged into one signal for my Verilog code? Is this done in Verilog? Is this done in the contraints file?


texts:
I hope the first part of this question isn't too physics based for this forum but I am trying to use an optical rotary mask encoder such as this one (Optical Encoder Pair Kit) to determine the RPM of a brushless 1:50 geared DC motor. The website above mentions that the package comes with 3 or 5 teeth wheels which correspond to 12 and 20 counts per revolution respectively and that for a geared motor you should multiply by the gearing ratio. I want to use the 5 tooth wheel to get the maximum resolution but I do not understand why using a 5 tooth wheel will give 20 counts per revolution. Why not 5, does it have something to do with there being 2 channels on the output?

To determine the RPM I am thinking that I will have to setup an interrupt in my microcontroller to add 1 to a variable (call it pulse counter) everytime the photodiode on the encoder spikes, then increment a revolutions variable when the pulse counter and the calculated number of counts per revolution correspond and then have a timer on an interrupt which will check the number in the revolutions variable, divide by 60 and output the result as an RPM value.

Is this a valid approach or is there a better way to do this?


texts: Charging lithium batteries while supplying power to load

texts:
So, the problem is that I want to charge (with 19.5v laptop charger) 4s config lithium batteries while at the same time supplying power to the load (In my case, portable speakers, but also want to use this setup for other projects). My original plan was to use a buck down converter with adjustable current and voltage to set the output to be about 2A @16.8v, suitable for charging. This means, when charging, the power will be spit between the batteries and load. I suppose this would be fine if the load wouldn't consume more than 30W.
If however it would be some 50W load, the batteries would not charge but discharge (cuz the current from supply is limited to 2A).
My solution for this is to create an extra path directly from power supply to the load with a 5 pin relay in between. When current is flowing from the charger, the relay would switch between the two paths, disconnecting the batteries from the load and connecting the power supply to the load.
I have no idea if this would work and neither do I know how to wire up the relay in this situation.
I also thought of using diodes on the batteries but diodes are mabye not a very efficient solution.
Any recommendations for an solution are very welcome. Thanks in advance!


texts: Wireless energy scavenging from in-home wiring EM fields

texts:
I was wondering if it would be possible to power a little 3.3V microcontroller, by harvesting an electromagnetic field around an in-wall insulated 240V 50Hz AC power cable.

Something like contactless inductive charging, like in an electric toothbrush.

Efficiency would be poor, but for a low power device may be an alternative to batteries.

Does the EM field only exist when there is a load on the wire or is it always there, regardless if there is any device connected?

A limitation would be the power harvesting device would need to attach to an existing straight AC wiring without cutting the insulation.
No coil on the "transmitter" side.

Is 50Hz way too low to be useful?

I came up with the idea after using a stud finder which has a little red LED that illuminates in the presence of live wires with a few cm range.


texts: What kind of DC motor is this and what does the circuit do?

texts:
I've had this motor at least for 5 years (salvaged from something) and I remember it working then. However it doesn't work now (5 VDC mobile charger) and so I opened it up expecting to see just the split rings. But I was surprised to find this circuit built in it. Why does it need that circuit and what does it do?
The motor body says - (If the picture is not clear)
6JS E 06 R
2400N 6V

Link to a better quality picture
http://postimg.org/image/l4unckkin/


texts: High voltage to low voltage conversion from multiple channels

texts:
There are more than 200 lines and every line carries voltages in the range of     0-36V.What are all the possible ways to convert 0-36V (pwm signal,5kHz) to 0-5V for ADC input?

Note: I should not use voltage divider directly on the line.


texts: Drive 3 5050 SMD RGB LEDs with 12v Lead-acid battery

texts:
I want to create a circuit to drive 5050 SMD RGB LEDs in my motorcycle which has power supply of 12V from sealed Lead-acid battery.

Spec for 5050 RGB LED is:

Maximum allowed forward current per LED is 20mA.

I want it be able to drive at least 3 LEDs in series, so essentially 3 branches since there are 3 LEDs to light up to get required color. Planning to allow to drop maximum 3.5V per Green/Blue LEDs and 2.3V for Red LEDs.

So, I assume my circuit should be able to deliver at least 10.5V (3 x 3.5V)

Since the power supply is Lead-acid battery. It may come down at safe level 11.8V. I thought about using LM317 and LM7812 but found they have high drop out voltage thus will not be giving enough voltage if battery is at 11.8V.

Are there better voltage regulators with low drop out voltage?

Or will it be possible build one with discrete components with not that bad in terms of efficiency?


texts:
What's the best way to quickly connect/disconnect ~22 AWG wires to a test jig pcb? I would like to use a spring loaded connector that can easily release the wire after I'm done testing. Currently have these

However they're expensive and don't hold the wire the best. I would like something similar to a fuse clip like this.

Does anyone know of any connectors that can accommodate this?


texts:
I am using a 3 Amplifiers chain for a Receiver system.

The required Output is -32dBm while the sensitivity of the system is -55 dBm,
I am able to achieve this.

But the maximum I/P power for the system is 0 dBm while my amplifier chain goes into saturation after -20 dBm and If 0 dBm is fed to the amplifier chain. It will definately cross the max. I/P power rating of the third amplifier which is +15 dBm.

The maximum O/P power which is allowed is 20 dBm for the receiver. Gain of my single amplifier is between 10-13 dB.

So I need to increase my tolerance for the maximum I/P power without degrading my O/P power level and Minimum I/P power.

Looking for an easy solution? Can I use attenuators but the problem with attenuators is that when I solve the problem of max. I/P power it will decrease the sensitivity of the system above -55dBm.


texts: Keep relay energized longer with capacitor

texts:
OK, I've found plenty of questions about relays where either the person wanted to have event 1 at time T trigger the relay at time T+delay (like flip a switch and have the relay energize 2 seconds later. Simple enough with a single-triggered 555 or such.) I've also found people who wanted a single event to trigger the relay but have the relay stay energized for a time after the event happened (so that a 1ms pulse from a MCU may cause a relay to stay on for 2 seconds. Again, simple enough with a cap connected to the gate of a transistor.) What I'd like is a good way to energize a relay that then kills the power to the WHOLE circuit and holds that for a bit longer.

Basically, the idea is for a watchdog circuit for a X Pi board. A 555 or a MCU (attiny85) could watch for pulses on one of the Pi's GPIO pins. When it fails to get the pulse in time, it energizes a relay that's NC so that it kills ALL power to both the Pi AND the watchdog. But I'd like to stretch that off-time out by a few more milliseconds just to make sure things have time to reset OK. So I can't use a cap connected to a transistor connected to the relay as when the power dies, it dies for the coil as well. I'm figuring a cap parallel to the coil would hold it for a brief time but what's the best way of wiring it to charge the cap (somewhat) slowly and also to keep it charged and the coil energized as long as possible after the power dies? The exact time it's held open isn't important so don't worry about the math and figuring out "well, a 1f cap and a 200ohm resister would hold it open for XXXX milliseconds if the coid resistance is 150ohm", etc. I'm just looking for the general circuit that would work best.

edit 1...
This is the basic idea of the circuit in mind (and yes, I didn't wire up the 555 completely here. I was mainly wanting to show the output and how the power would go to it.)
And to answer Bruce's question(s), when I say "as long as possible", I meant "given any set of available parts of arbitrary values, what arrangement would allow them to keep it energized as long as possible for that set?" So if the question was a simpler "what would keep a cap charged as long as possible in a circuit with a resister and yet still drain it?" the answer would be a simple series RC circuit without worrying about the size of the cap, the value of the resistor or what constitutes "as long as possible." I realize probably under reasonable sizes of a cap, I probably wouldn't be able to delay the relay more than a few extra microseconds so I'm not looking for a 2-hour delay or such.

The relay I planned on using is http://old.ghielectronics.com/downloads/man/20084141716341001RelayX1.pdf (basic stats: 5v relay, coil resistance about 50ohms, dropout around 0.5v.) So if my math is correct, a 100uf cap would be a 1RC of around 5ms, so that's about the longest I'd expect to be able to hold the relay open past its own operational delay with that sized cap. I do have a couple of 1f super-caps I could use as well but charging them may be tricky.

edit 2...
BTW, yes, I did leave out the flyback diode on my initial schematic (was just in a hurry.) The relay module I was planning to use is basically like this one (except that I only see one resistor on it, not two. Image is from http://www.electroschematics.com/8998/arduino-temperature-controlled-relay/)


texts:
I am working with PIC24EP256GP204. The CPU frequency is 64 MHz. I am generating two PWM pulses for TCD1304AP CCD sensor and two PWM pulses for WM8253 ADC AFE.

My problem lies with PWM pulses for ADC as i have to use ISRs to fetch data.

I need to sync Vsmp (it determines sampling point and frequency) and Master clock of ADC so that i can read the 16-Bit output of ADC (which is available in 4-Bit multiplexed format). I am generating square wave of frequency 3 MHz for Master clock of ADC and square wave of 500 KHz for Vsmp. I have verified the wave-forms with a digital oscilloscope.

But for syncing and reading the output of ADC AFE, i need to run some code in ISR of Vsmp and Master clock of ADC. If i just clear the interrupt flags in respective ISRs, then everything works perfectly. However, even a few lines of code in C programming language makes the PIC24EP hang. I couldn't post my whole code base as it is huge. I have posted ISRs code. Please have a look:

volatile bool vsmp_failing_edge = false;
// VSMP ISR
void __attribute__((__interrupt__, no_auto_psv)) _OC3Interrupt(void)
{
    vsmp_failing_edge = true;
    IFS1bits.OC3IF = 0;
}

// ADC ISR
void __attribute__((__interrupt__, no_auto_psv)) _OC4Interrupt(void)
{
    /*
    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();

    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();

    Nop(); Nop(); Nop(); Nop(); Nop();
    Nop(); Nop(); Nop(); Nop(); Nop();
    */

    if (vsmp_failing_edge) {
        // oc_disable(OC_CHANNEL_4);
        vsmp_failing_edge = false;
    }
    IFS1bits.OC4IF = 0;
}

The ISR _OC4 is assigned to Master clock of ADC which is running at 3 MHz and ISR _OC3 is assigned to Vsmp which is running at 500 KHz. The output of ADC is available at few other pins in 4-Bit multiplexed format.

ISR _OC3 is executed at falling edge of Vsmp pin. In the interrupt, i am setting some flag. After  16.5 Master clock cycles, i have to read 4 external pins at falling edge of master clock pulses. I have to read at four consecutive falling edges of master clock to get complete data.

Please comment on my approach or suggest better approaches for the sensor and ADC.

I also thought of using Pin change interrupt at Master Clock pulse output pin and some timer interrupt to fetch the data. However, i haven't implemented that approach because i am not sure if PIC24EP can handle the waveform generation and sync at the frequency i want it to.

EDIT:

If you look at code of _O4 ISR, you can find 60 Nop() instructions along with IFS1bits.OC4IF = 0; line will make PIC hang. I have added Nop() instructions to verify the number of instruction cycles required to make it hang.

The Nop() instructions are commented out. Without them, only the if condition and  IFS1bits.OC4IF = 0; line will make PIC hang. So, you can conclude that Nop() instructions are equivalent to just if part of the ISR in terms of execution time.


texts:
I have this circuit:

I know that D1 is cut-off and ID2=1.33mA. How can I find the V?

In the answer of this excercise it says that V=VΒ=-10+10*1.33=3.3V.
Is it correct? If yes, how did it come of and why is the V we are searching the same as the V in B?


texts: Is there a way to join metal to plastic?

texts: The plastic I would like to use is Polycarbonate, which will melt if you try to solder metal to it. If you can't weld the two, is there another way in which you can join metal to plastic? Ideally, I would like to build the circuit board into the polycarbonate itself.


texts: Power input smaller than output? How can this be?

texts: I am not an electrical engineer, and I was looking at the energy ratings of air conditioners and I'm having a hard time understanding why the output in kW is greater than the power input in kW. My understanding is that power input and output should be about the same in a closed system. Is this a terminology/marketing confusion? What do these statistics mean?


texts:
My goal is to program a FDM simulation of a transformer.  So, we have the coupled inductor model to start with ...

However, if L1 = 1, L2 = 9, and coupling is perfect then M = sqrt(1*9) = 3 and L1 - M = -2.

So, this seems problematical to me.  Also, if I try to simulate this model using SPICE, just for fun you understand, my goal is to program the sim myself, SPICE chokes on the negative inductor value and no output signal is generated.

I note that the model above does produce the right differential equations, that is,
v1 = L1*i1' + M*i2'
v2 = L2*i2' + M*i1'

However, if you try to simulate these differential equations directly, and the coupling is perfect, the the ratio L1 / M = M / L2 = sqrt(L1) / sqrt(L2) and you cannot solve them for i1' and i2'.  So, I'm stuck starting with these differential equations too.

One more thing - running the SPICE transformer model, i.e. specifying L1 = 1, L2 = 9, and k = 1, with a 1 v. 60 Hz input produces the expected 3 v. output.  However, changing k to .9 reduces the output to a few mv.  Even .99 and its still a few mv.  That seems very peculiar to me (I'm not an EE).

Any assistance would be appreciated.


texts: How does a maximum power point charge controller regulate the charging current, when it always draws the maximum current from the panel?

texts:
I want to understand exactly how an MPPT charge controller works and all I could find is this:

  An MPPT charger is a DC-DC transformer, that when it lowers the input voltage, it raises the output current as well, therefore, except for a small loss, the input and output power is the same.

But I also know that a battery bank needs to be charged in different steps having different voltages and currents (bulk, floating, ..etc)

So my question is that, if the MPPT charger always tries to get the most current out of the panel, how does it achieve those different charging steps?

Also, most references say that the output voltage is constant, so the control is done on the current, i.e. the output current is constantly compared to the maximum value and it alternates around a maximum reference value. How is the voltage constant - doesn't the battery voltage also change when the bank is charged and discharged?


texts: How to pick the most convenient mosfets for comparing switching capabilities and understanding SPICE2 simulation models?

texts: I have picked BS170 (signal application n mosfet) and IRFZ44n (power application n mosfet). I will tell the professor my decision is based on the fact that they both have very different power dissipation capabilities, input capacitance, gate turn on potential, and constructive parameters (channel doping, vertical structure, etc) due to their applications. I will be doing this using the PROTEUS 8.1 VSM. The objective is to use virtual simulation to prove some datasheet parameters. Can anyone give me their opinion with technical judgement? The only thing the professor said is "Use computer simulation to prove solid state physics, practicality and modelling theory of solid state devices in commutation operation. Am I getting myself into complex terrain? I need someone to guide me. Thanks in advance.


texts: How to measure if there is current between point A and B when source and grounding is unknown

texts:
I understand the headline makes little sense, so here is a clarification on what's going on.
I used thick steel rods to create a second floor (loft) in my apartment. Those steel rods are attached via long steel bolts in the (concrete) floor and the walls. My computer is right next to one of those steel rods. When I touch my computer housing (which is connected in a grounded 3-pin socket) with one hand and the steel rod with the other I receive some rather high AC voltage (even when the computer is off) - it's high enough that my arm is still "muddy" after 3 days. I also used an amplifier connected to the same outlet to replicate the experiment.
I am quite sure that the construction workers [when doing that steel-second-floor] hit a powerline, "closing a circuit" when I touch something grounded (the PC) and the steel rod at the same time.
In order to solve the problem I have to identify which circuit breaker is responsible for the powerline which is sending current to the steel-construction, so I can replace it. I'd rather not use my body as a "sensor" anymore - what other options do I have? I tried using a multimeter but to no avail(1).
Of course I had an electrician coming in today, but he was unfortunately clueless and just said to avoid touching electronics and the steel construction at the same time, but I believe living like that could pose potential bigger hazards.
Your support will be highly appreciated - I am a foreigner living in China, we got 230V here and as much as I like Chinese roast chicken I don't like to turn into one.
PS: I know the difference between static electricity, a 12V DC running through my body and AC hitting you - this is definitely AC on the rather stronger side as the side effects after two shocks are still present after 3 days.
(1) Setting the multimeter to AC voltage, connecting one end to the steel rod and the other to the computer housing shows 0 voltage.


texts:
Let's consider for instance a rectangular waveguide with TE01 mode.

As shown here, a possible attenuator may be realized with a metal card placed so that it is tangential to the electric field. Here the explanation of this behaviour.

There are some things I do not understand:

1) Why should it be placed with electric field tangential to it? I'd say that the reason is that a tangential electric field may induce a surface current that dissipates power on the card. But why does an orthogonal field keep undisturbed? I'd say that it would induce an orthogonal current inside the card, which also dissipates power.

2) Is that card a good conductor, a very good conductor, or a bad conductor? If it is a very good conductor, I understand that an orthogonal electric field does not induce current because current does not flow internally in a perfect conductor. But if it is a very good conductor, why do we have this big dissipation of current with a tangential electric field? It induces me to think it is not a good conductor, but just a resistor.


texts: How to make my own sequence of numbers and letters in a seven segment display circuit?

texts:
In this circuit, I have connected a single switch to a priority encoder, which is then connected to some inverters, further connected to a binary decoder, then to some current limiting resistor which is attached to 7 LEDs.

I'm trying to make it so that the LEDs light up in a sequence of numbers and letters.

I'm pretty sure the layout of my circuit is alright. I just don't know how to use the decoder to get my own sequence of numbers or letters whenever I press the switch.

If anyone could help tell me how that's done or if you think my circuits wrong, I'd be really grateful to know!


texts: I've recently moved to the Netherlands from the US and have researched the use of our lamps here.  In the US, we only used LED lights.  From what I have researched, I can use my lamps here with a power converter or an adapter.  I purchased several adapters and used some US LED bulbs and one worked for a few minutes and stopped working.  The other two seem to be working.  I have more that I have not set up yet.  My question is shall I purchase EU LED bulbs to use with the US lamps and EU adapters?


texts: issues with UART communication and a PIC processor

texts:
I have been working on enabling UART transmission between my PIC18f4620, a FT232, and my flash tool of choice.
Hardware wise - I don't see anything out of the ordinary (see below)
1

Yet with the provided code2 I am unable to receive anything other than ? in the COM receive section. This behavior is matched within coolterm as well. I have ensured the Tx/Rx are indeed flipped between the FT232 and the PIC processor, and I have double checked the baud rate matches the 10MHz crystal, still no dice. Any insight would be greatly! Thank you!
2

2
const unsigned char MSG0[] = "Transmitting... ";
const unsigned char MSG1[] = "Sent:";

// Subroutine Declarationsb
#include <pic18.h>

// Subroutines
#include        "lcd_portd.c"

#include <delays.h>
#include <plib.h>
#include <stdint.h>

void UART_TX_Init(void)
{

  BRGH = 1; // Set For High-Speed Baud Rate
  SPBRG = 65; // Set The Baud Rate To Be 9600 bps
  //--[ Enable The Ascynchronous Serial Port ]--
  SYNC = 0;
  SPEN = 1;
  //--[ Set The RX-TX Pins to be in UART mode (not io) ]--
  TRISC6 = 1;  // As stated in the datasheet
  TRISC7 = 1;  // As stated in the datasheet
  TXEN = 1; // Enable UART Transmission

}

void UART_Writes(uint8_t data)
{
  while(!TRMT);
  TXREG = data;
}

void UART_Write_Text(char *text)
{
  int i;
  for(i=0;text[i]!='\0';i++)
      UART_Writes(text[i]);
}

 uint8_t UART_TX_Empty()
{
  // Check the output (transmitter) buffer emptiness
  return TRMT;
}

void Wait(unsigned int X)
{
   unsigned int i, j;

   for (i=0; i<X; i++)
      for (j=0; j<609; j++);
   }

// Main Routine

void main(void)
{
UART_TX_Init();

unsigned int result = 0;
   unsigned int i;
   unsigned char C1, C16, C256;
   uint8_t Data = 1;
   TRISA = 0;
   TRISC = 0;
   TRISB = 0;
   TRISD = 0;
   TRISE = 0;
   TRISA = 0;
   TRISB = 0xff;
   PORTC = 0;
   PORTD = 0;
   PORTE = 0;

   ADCON1 = 0x0F;

   LCD_Init();                  // initialize the LCD

   LCD_Move(0,0);  for (i=0; i<20; i++) LCD_Write(MSG0[i]);
   Wait_ms(100);
   LCD_Move(1,0);  for (i=0; i<5; i++) LCD_Write(MSG1[i]);
   while(1) {

if(RB0){
uint8_t Data = 1;
Wait_ms(100);
LCD_Move(1,5); LCD_Out(Data,1,0);
}
if(!RB0){
uint8_t Data = 0;
TXREG = Data;
Wait_ms(100);
LCD_Move(1,5); LCD_Out(Data,1,0);
}

UART_Writes(Data);

    }

}

[EDIT]
Configuration Bits

This project is coded using MPLAB IDE v8.92


texts: How to generate 1Hz to 40Hz Waveform by ATMEGA32U4 (Arduino Board)

texts:
I am using ATMEGA32U4 (Arduino board ). I am facing problem with TIMER. I want to generate 1 Hz to 40 Hz signal in two pins and change PWM signal with certain period of time.

Example:

TIME | PIN9 Freq. | PIN9 PWM | PIN10 Freq. | PIN10 PWM | Alternate Mode
T0   |    2Hz     |      50% |         2Hz |       50% | 0
T1   |    3Hz     |      50% |        15Hz |       20% | 0
T2   |   30Hz     |      40% |         2Hz |       50% | 0
T3   |    2Hz     |      50% |         2Hz |       50% | 1

Alternate Mode activate gives 180 degree phase shift b/w PIN9 and PIN10.


texts: Calculating max wattage load for opto-triac

texts:
Are there any guidelines?

Do the guidelines differ depending on resistive/inductive/reactive loads?

For example, the Vishay VO2223A is rated up to 1A. At 110V it seems it can switch up to a 1 A x 110V = 110 watt load. I saw some training material that indicated only up 22W load. Is this derating for safety? Is it to cover startup current draws?

I'd like to independently switch several AC devices: 50W heater, 23W CFL, 4W water pump.


texts: Mounting PCB in extruded aluminum housing

texts: For a small hobby project and to learn a bit about electronics, I would like to make a DC/DC uninterruptible power supply.  I really like the look of the extruded aluminum cases.  However the off the shelf PCB I am looking at is smaller than the batteries.  My question is are there mounting options for PCBs that are smaller than the extruded aluminum housing?  If so what are they and where can I find them?


texts: BJT with collector base or base emitter shorted

texts:
People have been using BJTs in various configurations with either of the junctions shorted. The following queries persist for these configurations. Links to previous questions are added

1)Base collector shorted
This configuration is used when the bjt is to be configured as a diode. Now, what would be the ratio of the base current to the collector current is this configuration and does this have any relation to the standard Hfe

2)Base emitter shorted
Mentioned as an alternative to using zeners. In that case can I use a BJT with base-collector shorted and reverse biased in replacement for a low voltage zener. (in place of standard zeners which have a soft knee, saw this link which mentions a sharp knee for this config). Say for example I use a BC817 as a replacement for a 5V zener. And in this case I expect the current rating to be the lower of Ic and that dictated by the power rating of the device


texts:
I couldn't really figure out this issue. Raspberry Pi 2 has 1GB of RAM, 900 Mhz Quad Core ARM Cortex-A7 processor and so on. On the other side we have Cortex-4 processor 256Kb RAM. Other peripherals also points to Raspberry pi. However they have almost the same price.

Please do not judge me, because I think I am missing some point here and I think there is a reason it is so. Can someone enlighten me in this topic please?


texts: Measure Battery voltage with ADC in noisy environment and supply circuit from that same battery. single ended/differential mode?

texts:
need your opinion:
Want to build a device that is able to measure a battery voltage and send results wirelessly every x minutes.
The Battery has nominal 24 volts. Batteries are in a yacht (e.g. engine batt, generator batt, service batt, bow thruster and stern thruster batt).
The ADC could be a ADS1115. circuit should be powered by that same battery. I made two variants shown below and like to hear your input what would be the most robust solution in terms of accuracy and resistance against noise.
Variant 1: single ended mode
The battery would feed an LDO which makes VCC 3.3v, and to measure the Batt voltage it is divided to get 0..3V range, and feed that to A0 of the ADC which is configured to single ended measurement.

Variant 2:
ADC used in differential mode. Batt GND and plus are fed into a voltage divider which makes a voltage of 0..3V, which is symmetrical within but not touching GND and VCC levels of the ADC. That is fed into A0 and A1 of the ADC and measured in differential mode.
All GNDs of uC, ADC, LDO, Battery are connected to each other as in first variant.
Question is which variant gives more resilience against noise on the power lines to which the battery is connected, or if there is an idea to make it better than shown.

A third option I thought of was to power the circuit with two AA batteries (it draws only 1-2 µA in sleep mode) to be independent of the Battery GND, however the measurement anyway would only work if GND reference of the signal and of the ADC are the same, so Battery powering does not make an improvement.
Thank you!!


texts:
I have read various questions and posts, but still I am not sure whether when talking about resistors, thin film means the same as metal film or not.
I read the statement that "most of the metal film resistors are thin film". That means that there are also metal thick film resistors. But does it also mean, that a thin film resistor is always a metal film type?
To give an example: Are those resistors from Yageo (http://www.yageo.com/NewPortal/yageodocoutput?fileName=/pdf/R-Chip/PYu-RT_1-to-0.01_RoHS_L_9.pdf) metal film resistors?
The "resistive" layer is not specified further in the datasheet, but since the Yageo website talks about "sputtering" I assume it´s metal film?
EDIT: From the comments it seems that "thin film" and "metal film" is often used as a synonym. This seems to be the case because metal film resistors are produced by thin film techniques.
Open question seems to be therefore: What is the difference of through-hole(i.e. leaded) metal flm resistors and thin film smt resistors (beside of power and voltage rating)?
Is (in general) a leaded metal film resistor comparable to a thin film smt resistor with regard to noise? If not why not if the process (thin film) and the materials are the same?
//Update 2020_12_31: TO close the question with the outcome from the omments/discussions. Thin-film resistor are simply one sub-category of metal-film resistors.


texts: Turn on transistor with output from sound card

texts:
I want to turn on a transistor by playing sound through my computer's soundcard. I thought that this simple circuit with a diode to rectify the AC, capacitor to smooth it out, and a transistor to switch would work.

simulate this circuit – Schematic created using CircuitLab

But it didn't work. What's going wrong?

Note: What I'm actually trying to do is trigger the PTT on a Yeasu FT-60R hooked up to my computer when the computer starts playing sound. My plan is to use one audio channel as the audio input to the radio, and the other input to drive this circuit. The transistor would connect the radio's MIC line to GND through a 2k resister, which is supposed to trigger PTT. The LED circuit is just to see if the idea works at all.


texts:
Recently, I am working with amplifier circuits but circuits available online for an op-amp have some extra components with respect to what we learn in textbooks.
I know the basic amplifier components and their functioning, for example, Feedback resister, decoupling capacitors and I know how we control the gain, what is inverting and non-inverting input, and all other aspects which we learn in basic op-amp circuits. For example,

Now, can anybody please explain why we are using some extra capacitor, diodes, and resistors (C1, C2, R1, R2, C3, R3, D1, D2, R6, C4, C5) in the following TDA2030 amplifier circuit.
What do they do? Why we are using them in the circuit? How changing the values affect the output? etc. These questions will help me and others to gain practical knowledge and modify the circuit by our own understanding.
Please Note:

I know how the capacitor, resistors, diodes, op-amp, etc works. I know basic electronics.
I know that extra components (C1, C2, R1, R2, C3, R3, D1, D2, R6, C4, C5) are used to control the noise and improve audio quality.  But, I want to know even more.
Please don't comment on why I am using TDA2030 IC.

Thank you


texts: Why is this the maximum dynamic range in a spectrum analyzer?

texts:
In Keysight's popular AN 150 there is a plot of noise and harmonics amplitudes versus the level of the input signal at the mixer (page 57).

It's stated there that the maximum n-th dynamic range is given at the intersection of the noise and n-th harmonic lines (i.e. when both noise and the n-th harmonic are of the same amplitude).

I'm having a hard time understanding why this is so. As I see it, one can change then level of the mixer's input to perform some kind of trade-off between SNR and harmonic distortion. So what criteria is followed to state that when both effects are equally relevant the dynamic range is maximum?


texts: Sharing the low voltage rail of unknown potentials... How to make Proper Floated Voltages?

texts:
I asked a previous question about running circuitry off a high voltage supply with unknown ground potential.  The question is here:  Generating a 10 volt rail from a High Voltage Supply with unknown Ground Potential

Based on the excellent answers, I realized I may have been making it a bit hard on myself.  I have a new question:

Let's assume we have a high voltage source as a large capacitor bank at 200 volts.  I have a 12 volt battery I want to use to run an NE555 and a mosfet that is switching the 200 volt circuit.

But let's make it more complicated by assuming I can't guarantee that the 200 volts across the cap is +200 and 0.  It might be +100 and -100 (or even +10 and -190), whereas my battery might be +12 and 0 relatively speaking. I need to guarantee that I have 12 volts between the gate and source of mosfet so as to not damage it.  The question is:  If I simply connect the 12 volt battery right into the circuit, will its low potential automatically match up (Float?) to the low potential on the high voltage circuit, thus guaranteeing a 12 volt difference to between the Gate and Source of the mosfet?

And for a more advanced system:  What if the 12 volts isn't even supplied by a battery?   What if it's just another capacitor bank?

And for a really complicated system: What if I use the 12 volt and GRND rails from a Switched Mode Power Supply like a homebrew ATX power supply?  I tried something like that a long time ago.  But I was using rectified power from the 120v 60Hz Mains and filtering it into a capacitor.  Then I attempted to share the ground rail with an ATX power supply and I ended up destroying the power supply (smokes and sparks!).  I never did find out why, but it might have had something to do with the fact that my SMPS and main circuit voltage were both sharing the mains... thoughts?


texts: Connect STM32 Ethernet to PHY - clock signal

texts:
I want to connect MAC available on STM32F745 to KSZ8041FTL (PHY) via RMII.

I will clock PHY from external 50MHz clock generator, connecting clock to the REFCLK input of PHY.

But what about STM32? Should I also connect 50 MHz clock to the STM32? If yes then I guess I should connect it to the RMII_REF_CLK input (PA1)?

Can I just connect output of the clock generator to both IC?


texts: How to measure the output impedance of a valve preamp?

texts:
I was trying to measure the output impedance of a DIY preamp for the past couple of days without any luck. Each time, I got to the same result of around 3K3 ohm, which is unbelievably low.

This is the circuit I’m working with:

I’m using the book “Designing Valve Preamps,” by Merlin Blencowe as a reference.
What I have tried:

Connecting a resistor to LTSPICE circuit and finding its value at 50 % output gave the output impedance around 3250 Ω.
The author mentioned that theoretically if you were to feed 1 V signal into the output, the ratio between the forced voltage and the current drawn will give you the output impedance. This gave me again around 3K3 Ω.
I have replaced the potentiometers by fixed value resistances, and simplified the circuit as shown below:

Then, I have used Merlin’s Thevenin equivalent for the gain stage (page 31), I tried both for bypassed and unbypassed capacitors, which resulted in:

Now, coming to basic circuit analysis, I have tried 2 ways:

a) set all capacitors as short circuits
b) treat the capacitors as complex impedances.

Both of those ways resulted in a total impedance of around 3K3 Ω.

This is impossibly low since It means the signal transmitted almost ideally to the amp. However, when connecting it to a high Z input and attaching a cathode follower in between, the sound seems to have more “breathing space”.

Was I on the right track? What have I done wrong?
If not, then how do I calculate the output impedance of a preamp?

Any help is greatly appreciated.


texts: Bridge rectifier output voltage at no load?

texts:
(First posting)

I am building a simple PSU with a torroidal transformer and bridge rectifier. I'd like to know the output DC voltage from the rectifier while under load. e.g. charging a battery.
I see that the formula is in here but these things do my head in (sometimes) so if I quote the numbers some kind souuratingl may help.

The transformer is labelled as being 22 VAC at 16.9 amps but at a less than constant  duty cycle I fear. It is centre tapped and grounded.  At least there's a green etc. ground wire along with the red and yellow secondaries. However, my DVM is registering 28 VAC and the DVM if not Fluke, isn't rubbish no worse than 2-5% I'd say.

Connected to a bridge rectifier rated at 1000 V and current rating > 20 A, what DC voltage should I expect to see with/without a resistive load?


texts: What is reference voltage in a D/A converter

texts:
When I searched on the internet what I got as an answer for the above question is that the reference voltage means the highest voltage tha D/A can output.

But my lecturer at college did a calculation as below.

  An 6 bit A/D has values 110101.
  Reference voltage is 0.25V.

Then he multiplies each bit with the two to the power of corresponding to the position and multiply it with the reference voltage. The final value (Vout) is 13.25v. If the definition at the beginning is correct this can't be true since this value is greater than the reference voltage. What does reference voltage mean according to this context?


texts: What is this component from an old thermostat?

texts:
I recently cannibalized an old thermostat for parts, and found a strange looking component with no markings at all.

Here's a picture (since I can't figure out how to describe it):

My first guess was that this was some sort of resistor, but I can't seem to measure any resistance across it with my multimeter...

I'm very much an electronics newbie so please excuse me if the answer is obvious :)


texts: Hey everyone I am working on a project that is a lot harder than what I thought. It is a project for school. How can I detect a gunshot indoors without using an array of microphones? I had something going well with using microphones, but I would be breaking patents which I cannot do for this project.


texts: What is the purpose of this op amp configuration shown?

texts: I've been researching common amplifier configurations, but the only ones with positive feedback that I have discovered is a negative resistance simulator, however that has negative feedback too.


texts:
I have a comprehension question regarding the design of a reverse phase dimmer. I have a picture attached of the part of the circuit I do not understand:

The line is connected to the Drain of Q2 and the load is connected to the Drain of Q3. The sources are connected together and the gates are driven by an IC or MCU. So I understand that the complete sine wave can pass the series transistors. Now what I do not understand is why the GND rail is connected to the source of the AC path between the sources of the MOSFETs. Would that not induce high voltages on the GND rail and destroy the low voltage components like the IC or MCU? Or am I getting this completely wrong...
Thank you very much for any kind of answer!


texts: Portable Guitar Amp - Distortion, Volume & GND

texts:
I have tried following the given schematic

There are 3 things I am unsure of (what I tried):

The Volume 5k Potentiometer:
I have tried adding a volume control to the schematic by placing the potentiometer parallel to the Dip Switch. But i am unsure whether this is what has to be done. Could someone help me clarify this?
The Distortion, The instructions stated that we could go up to 10uF but i have added an 8 tone dip switch with 22, 33 and 47 uF additional capacitors. Is this acceptable?
The GND
I am completely unsure how to connect the earthing (ground). Do i connect the negative wire to the GND but wouldnt that just short the sleeve and the ring according to the schematic...
EDIT: As indicated by Anonymous, the shortage will provide the GND.

I also added an led paired with a 470Ohm resistor parallel to the inputs to indicate whether it is working or not.

I am a novice guitar player and wanted to build a 0.5-1W amplifier for the same. but i have little previous experience in Electronics. I would be immensely grateful if somebody could guide me and help me out on this.

Thanks & Regards


texts: How to probe into the internal signals and registers in FPGA without using JTAG?

texts:
I am using a Xilinx Spartan 3E FPGA kit in my academic project to synthesize a design comprising of a couple of 32 bit internal registers (eg few counters, shifters and some configuration registers) . There is no direct access to the registers using the input/output ports of the design.

My design is in Verilog. Is there any way to probe the values written in the registers through Xilinx ISE tool?

Should I use chipscope for this purpose? For verification, I want to check the internal values in the registers.

I do not have JTAG cable, I am using USB connector to interface the kit with Xilinx ISE.


texts: Measure duration of a non periodic message on FPGA with VHDL

texts:
I'm trying to measure the duration of a non periodic signal(message) on FPGA, as below :

I want to measure the duration of the measured signal by counting the number of reference clock's period. I set the first rising edge as the start trigger, but how should set the stop trigger?

I have no idea how to do this, can you give me some advice?
I want to implement this on FPGA with VHDL.


texts: Trigger digital interrupt on negative voltage

texts:
For a little project of mine (FPV OSD for Quadcopter Camera) I need to detect every time the signal voltage goes negative. The Signal I get is NTSC. Here each line sync is marked by the voltage going to about -0.3V. The OSD itself will be realized using an ATTiny, which can't read negative voltages. Also, the ADC on the ATTiny is by far too slow to detect that short line sync time. For this to work I will need to use a digital interrupt.

So I nees some kind of circuit, that detects every time the Voltage dips below 0V and turns that into a HIGH (>0.7V), while it stays LOW if the voltage is above 0V. This should work fast enough for NTSC (so should be able to work at at least a few megahertz).

I am basing this on an existing open source circuit that currently uses an LMH1980 (for line sync detection) together with an ATTiny13A (to render the actual OSD), which (the LMH1980) is comparatively expensive and bulky. I think it should be possible to replace the LMH1980 wih a cheaper and simpler circuit to detect negative voltages (=line syncs) and have the existing ATTiny do the then trivial work of detecting line and frame syncs.

I would prefer the solution to use only standard components and be as small and simple as possible.

Edit: One design constraint that I forgot to mention is that the solution should impact the video signal as little as possible to not introduce image artifacts, since the video singnal will also be sent over a video transmitter and viewed by the pilot.


texts:
This question is a little bit stupid and silly.

As I am chemist, I don't remember electricity physics very good. As I remember it shouldn't harm anything, but I need to be sure.

LEDs will be blinking sometimes together. But not longer than 50ms.

They will be parallel for only short time. Because they supposed to blink reporting 2 modes 1st - normal, 2nd - error. And switching between them can be no longer than 50ms.

simulate this circuit – Schematic created using CircuitLab

I use resistor for both LEDs, but it just curiosity question.


texts: How to automate continuity tests on harnesses with up to 200 connections

texts:
I have some dozens of wiring harness, and always buying more. Nowadays I need to test connection by connection through continuity test with a multimeter and checking on the documentation in order to verify if each harness were build correctly. I definitely need to find a way to make it automatically. That's why am here... Please bring me ideas how I should design a circuit to accomplish that.
A few considerations:

Each harness can have between 40-200 connections.
Each harness has one automotive connector at one end, and a few hypertac connectors at the other end.
At one end, each harness has only one automotive connector w to 200 pins each (rarely fully used)
At the other end, each harness has a few hypertac connectors w 90 pins each (sometimes fully used)
I do not have many resources, that means the solution should as cheap as possible.

Doing this manually, I check on the mapping doc then I test continuity b/w the two pins, but to do it automatically the hardware must have to test each pin at one end w all pins at the other end. I think it should be like a switchable loopback between several pins.
Comes in my mind to using 90+200 = 290 relays and control them w I2C, but it does not look a good nor elegant idea to have this rude amount of relays operating.


texts: Precharging capacitors with P mosfet slew rate control - Unwanted turn ON

texts:
I am considering using a MOSFET to control the dV/dt rise (slew rate) when power is first applied to a DCDC power supply.

This will hopefully resolve both a precharging issue I am having and the fact the DCDC (LM5008) is breaking if a high dV/dt is applied.

Circuit
The circuit is mainly taken from the ON-Semi appnote. With the addition of a zener to protect the gate voltage from getting too large.

Problem
1. The simulations shows a high current spike (time 50ms), I believe this is cause by the MOSFET gate and C1 charging/floating up to the supplied voltage. Any ideas how I could mitigate this unwanted turn-on of the Mosfet?

Consulted Documents:

The motorola appnote everyone refers to MotorolaAN1542
Similar ON-Semi appnote about a PMOSFET implementation AND9093-D


texts:
I have some SMDs from a board which I am not able to identify. On top of the ICs is the marking:
OULO- SOT 23-5 (I'm not sure if they are zero or O.)
In the picture U4 and U5 are the OULO component.


texts: How is machine code handled by the microprocessor?

texts:
And no I don't mean "How do you write a program for a processor".

What I want to know is how does a processor interpret some aribtrary instruction, say 100001 as ADD r1,r2 etc.? What do the individual bits in the bit sequence mean and how does the bit sequence tell the processor what to do?

Is it similar to how an FPGA works? Is the processor logic just a bunch of gates?


texts:
I was given the task to make a new version of a board which have this little contraption for RS485 termination resistors:

simulate this circuit – Schematic created using CircuitLab

My question is, does this really work? I my concern is that the body diodes will mess things up.

I have seen that some manufacturers offer RS485 driver chips with a termination resistor that is possible to enable/disable, however theese doesn't match the required resistance in my application.


texts: What is the reason for compensation at async generator outputs?

texts:
I see capacitor banks are installed at async generator outputs. What is the function of compensation in this case? I thought compensation was done at the consumer and for induction motors.

Can this be explained by using phasors and reactive and active power concepts?


texts: How do bluetooth headsets handle 2C charging current?

texts:
I have used a few of those bluetooth headsets that are wireless stereo (TWS) ones and are charged by a case in which you insert them. I haven't used expensive ones, just rebranded chinese ones. All of them seem to get fully charged to 100% from 0% within 30 minutes. The case shuts off charging in 30 minutes and the phone displays 100% battery of the headsets.
So it seems the tiny 30 mAH or so lithium ion polymer batteries are charged at 2C charging current, which I doubt, even the highly advanced batteries of Tesla cars can't accept. How do these bluetooth batteries manage such high rate of charge?


texts: Common Mode Noise filtering for Diff Mode Circuit

texts:
I have a circuit that has only two pins and there is no earth ground.
However, I have to test it for BCI and design a common mode filter with diff mode.
Designing diff mode filter is simple but common mode without earth ground is very complicated, or it is for me. The circuit has a buck converter and the frequency is 250KHz. What kind of filter should I design?

simulate this circuit – Schematic created using CircuitLab


texts: Why don't we talk about a signal reflection when we treat a lumped element model of a circuit?

texts:
I don't clearly understand why I have never seen a talk about a signal reflection in a lumped element model.

When there is a transmission line connected to circuits A (signal emitter) and B (signal receiver) at its ends, we talk about the signal reflection when ZA (Thevenin equivalent series impedance of A) and ZB (equivalent impedance of B) are not matched to a characteristic impedance of the line Z0.

However, when the line is so short compared to a signal wavelength on the line, we ignore the line and see the whole circuit as "A is directly connected B". This is a lumped element model of the whole circuit. In this case, we don't say there is the signal reflection when ZA and ZB are not matched.

It seems the signal reflections only occurs between the transmission line and circuits it connects to. Could you please tell me why?


texts: Reasonable CPU power usage for solar panel powered system with battery

texts:
I am building a system using an embedded board that appears to use about 1/4 to 1/3 AMP according to my bench power supply. Is this low enough power consumption for this system to be run off of some battery(s) charged by a solar panel no bigger than 3'x 3'?

EDIT: Why the down votes? Is it not a reasonable question? I'm not really an electrical engineer and I've never worked with solar panels before.

More details:

1- The board will be "active" for about 10 hours a day.
2- Board uses 5 volts.
3- I'm probably not understanding what my bench power supply is telling me about power usage. Each supply has an "AMP" reading in the form of X.XX and is currently reading about 0.22. I "assusmed" that meant the board is drawing nearly a 1/4 AMP. However the documentation for the board says typical power usage is about 250 mA.
4- The board is an Olimex SAM9-L9260 ( AT91SAM9260 ) that is sitting running Linux and sending output to a serial console as fast as possible ( counting ).


texts: Need help for calculation of this capacitive power supply

texts:
Look at this circuit. It's an almost complete capacitive power supply with necessary part.

simulate this circuit – Schematic created using CircuitLab

I have trouble calculating:

the input capacitor (whose reactance does the main job reducing input 220v AC voltage)(C1)
the input resistor (I am not sure why they put this. but I think it's because the smoothing capacitor needs a lot of current to charge at first. the resistor lets it charge slowly and not take a lot of current.)(R1)
the series resistor before the zener diode (I think it act a a current limit)(R3)
and finally the capacity of smoothing capacitor.(C2

The values "X" mean they are given. And "?" means I don't know.

Let output voltage "Vout" and output current "Iout". Also the zener diode breakdown voltage "Vzener" and the capacity of C2 "Csmooth"
and the "Cin" is the input capacitor capacity and "Rin" is the input resistor resistance.

The R2 is the discharge resistor for C1 and discharges it when input AC voltage is removed.

please give me a way using formulas to calculate those parameters I mentioned while the values: Vout, Iout, Vzener are given.


texts:
I'm a new electrical engineer so bear with me. I hear some of the other engineers I work with talk about a race condition that exists in one of our circuits.

What does that mean?


texts:
In the datasheet there is this shematic how to dual power 18F4550. However they don't specify which transistor to use and what resistor values have to be. For capacitor I use 100uF (diode side) and 470nF (Vusb side). I tried putting in whatever BJT I have at home but it did not switch to Vbus when no Vself available.

Could someone please suggest which BJT to use (model no.) and which resistors should come with it. BJTs are like a dark forest for me.


texts: DDS - find optimal size for LUT, PHACC and sampling freq for application

texts:
I had the following question.
About the topic of DDS you can find a bunch of information on the net and i think i understood the basics relatively well.
You use a lookup-table with stored values of the function you want to put out. Then you increment the value of an accumulator periodically and put the value from the lookup table which index is according to actual value of accumulator to your DAC.

What i'm missing a bit in most of literature i read about this topic is how i find the most suitable size of Lookup table and phase accumulator for my application. Also i'm not sure how to find out most suitable sampling frequency or more precise the right amount of oversampling.
If you look at basic formula: f(out) = [tuning_word * f(sampling)] / size_of_accumulator
You can determine that tuning word is the variable size you use to set up your desired output frequency.
If you would increase sampling frequency you could use smaller tuning words but i don't think it would make sense.
The higher the sampling frequency is over the sampling theorem (2*signal_freq) the better the quality of my output signal gets, so sampling frequency should be as high as possible ?
The higher my accumulator is, the more increments can be done before it is filled which means accuracy get's increased so choose accumultor as big as possible also ?
Or is it more the size of lookup table defining the accuracy or both of it, so make both, the lookup table and the phase accumulator as big as possible and choose tuning word accordingly to reach prevailed number of increments ?
Or what is the criteria you are using to determine these parameters implementing your DDS ?
Greetings


texts:
I'm quite new to the world of electronics, and so I need some newbee-help.
I've got an Arduino uno, and I've recently bought a LPR550AL pitch & roll gyro.
(if it helps detailed info can be found here http://www.electrozone.dk/1550)

Obviously I read the description and the datasheet, but green as I am I don't trust that I understood it all properly.
I'm uncertain about how I should interface the gyro with the arduino. The datasheets talks of external low- and high- pass filters which, quite frankly, I haven't a clue what means.
Furthermore, the board has a 3,3 volt regulator which leaves me uncertain whether to use that or the arduinos 3,3 volt pin on the gyro-boards vin pin.
The datasheet also mentions that I should short the selftest pin to ground, should I do that?
The description says the same thing for the power down pin.
I assume the power down pin will, well, power down the board?
Can I even do that from one of the arduino pins? It occurs to me that they operate at 5 volts, and not 3,3.

Advice in general will be well received.
Same goes for resources for further reading/learning.
I should also be grateful if someone could give me instructions to connect this without burning anything :)

One final thing: Am I right in assuming that the difference between the vdd/3,3v input and VIN is that VIN is non-regulated?


texts:
I'm new to electronics and am trying to make a night vision circuit. A similar question has been asked before, but with priority on efficiency. I want to control a 700mA-1000mA IR LED using a 5v input and an ESP8266 microcontroller as part of a night camera project. The LED should be able to be switched on/off from the MCU and will be off most of the time.
One solution is to use a dedicated LED driver / constant-current power supply, which is expensive (e.g. this LED driver for $7+shipping). Another solution is to use a single high wattage resistor, which is very inefficient. See:
How to drive high powered LEDs as efficiently as possible
How to drive high power LED and Arduino by the same power source?
I'm looking for a method of driving the LED using components that I can get cheaply (typical Arduino hobbyist components - a quarter watt resistor multipack, a transistor multipack (e.g. with BC337 and 2N2222 NPN transistors), buck/boost converters, the microcontroller itself).
LED specifications
These LEDs: https://www.aliexpress.com/item/32810764742.html
Forward Voltage: DC1.4-1.6V
Forward Current: 700-1000mA
Simple resistor method
My first thought is to use a current-limiting resistor. Then, from R=V/I we get R=5/0.7=7 ohms. From P=IV we get P=0.7*5=3.5 watts. I only have quarter watt resistors (and 3.5 watts sounds like a lot of power to dissipate), so this solution is not desired.
2-transistor method
I read about a method of limiting current using 2 transistors (schematic attached below).
Source 1 http://www.physics.unlv.edu/~bill/PHYS483/current_lim.pdf
Source 2 https://www.homemade-circuits.com/universal-high-watt-led-current-limiter/
This would satisfy my requirements of being a cheap solution and using simple components. I have BC337 and 2N2222 transistors. I think the BC337 can handle 800mA, with hFE being 100-630 (info for BC337 here). In the sources, they use an hFE value of 30. How do I know what value to use?
Questions

How to choose hfe?
What values should be used for R1 and R2?
How much power will the BC337 transistor need to dissipate?
Is the sensitivity to temperature tolerable? (e.g. 0-30 celsius)
The ESP8266 can output a PWM signal. Would this be useful for the circuit?

Here is my attempt at a schematic. This doesn't yet incorporate switching using 3.3v logic from the ESP8266.


texts: Is it necessary for EM fields to be dependent & co-exist in static conditions?

texts:
I was having a discussion today with one my colleagues in the lab about the independence and co-existence of EM fields.

My argument:

In time-varying fields: EM fields are necessary dependent, and they have to co-exist. They get coupled through the time derivatives that appears in Maxwell's equations.
In static fields: EM fields are independent and each can exist separately or together.

His argument:

In time-varying fields: (similar to mine)
In static fields: EM fields must co-exist. (He is mentioning the spin of the electron about its axis of rotation, and the rotation of the electron around the nucleus and how that induces a magnetic field.)

Examples to clarify my question:

A point charge at rest (for simplicity), has a static E-field around it pointing in the radial direction. (is there a magnetic field?)
A DC current flowing in a conductor produces an M-field around the conductor. (is there an electric field?)