texts: Managing BOMs in production management systems

texts:
I'm looking for a good way to manage BOMs for electronics assemblies in a production management system.
I would really like to hear about how others manage BOMs in a professional setup.

I'll start by describing our current situation an why it doesn't work very well.

We are using the OrCAD Capture CIS/PCB Editor for schematic capture and PCB Layout. The BOM generated by Capture is imported into Microsoft Dynamics NAV, which we use for production management/planning, economics and stuff.

The BOM is stored in NAV as a summed list. I think it is called as instances in OrCAD terms. Each part instance is stored with a part number, what quantity is needed, an the RefDes of the occurences in one or several text fields.

NAV has a certain amount of space in each field. If the list of of RefDes' is too long, it is broken into several fields. The list can be broken in the middle of a RefDes, so the first characters is at the end of one field and the rest in the beginning of the next.

That way is really good for procurement, since they know how many of each part they have to purchase.

The problem is when we generate a BOM for the external EMS. They need a BOM with part numbers and RefDes, so they can map the correct parts to the pick'n'place file for the assembly.
The BOM exported from NAV is a procurement BOM in a weird excel sheet where the RefDes is listed in several cells like described above.

Problem is that the EMS has to manually combine the cells, to get a complete list of RefDes. This is tedious and prone to errors since it is a manual process.

There must be a better way to do this.

It could be a problem our NAV configuration/setup, but my current conclussion is that NAV is pretty useless for electronics production.

I have seen systems where each occurrence of a component has its own line with partnumber and RefDes in the BOM. This would be a manufacturing/assembly BOM.

It satisfies the need of the EMS, and i bet the "system" can sum the the occurrences of each part so procurement is satisfied as well.

What are your experiences with managing BOMs for production and procurement?

Which systems do you use?

How are the the data stored (by instance or occurrence)? And why?

Is one way preferred over the other?

Any thoughts are appreciated.


texts: CAN - Tranceiver @ 5V VS Tranceiver @ 3V3 Immunity

texts:
I would like to change a 5V CAN transceiver on my board into a 3V3 CAN transceiver. Nevertheless as I am clearly not a specialist of the CAN protocol, I am afraid of doing a big mistake ! I think it will clearly make the communication less robust if I reduce the power supply to 3V3. The rate of error of communication will increase. In 5V I have already some errors.

Here are the two differents datasheet (If you know a better 3V3 CAN transceiver, I would be happy to hear it) :

3V3 transceiver : https://www.ti.com/lit/ds/symlink/sn65hvd232.pdf?ts=1591434105120&ref_url=https://www.ti.com/product/SN65HVD232

5V tranceiver : https://www.onsemi.com/pub/Collateral/AMIS-30660-D.PDF

Well what I see is the differential voltage and the common voltage between CANL and CANH is lower with a 3V3 tranceiver during the dominant and the recessive...

Transceiver 3V3 :

Transceiver 5V :

Actually, according to the datasheet, the differential voltage is not really affected ? ! And the voltage refered to the ground is a bit affected but no much as I thoough... What do you think about the difference in robustness between the two transceiver ? What are the other elements to pay attention ?

Thank you very much and have a nice day  !


texts:
I want to learn how to demodulate a 38 kHz IR PWM signal.(Such as that transmitted by a TV Remote Control) I know it can be demodulated easily using a TSOP1738 IR receiver.

I realize that the TSOP1738 can be much more easily implemented, but how is the signal demodulated inside the reciever ?( I am not planning to build a demodulator, just curious how it works).

I searched online but couldn't find the mechanism anywhere. I looked at the datasheet and the block diagram just shows a demodulator but not how it works.

(I have attached the block diagram in case it helps)

Edit : Typo in the title


texts:
So I was working on the switch backlighting for A switch plate on my boat. There is a single led mounted in a light bar that mounts behind the engraved legend plates.

I bought a replacement led at RadioShack. It is a red 800 mcd LED. The package says 1.7V - 20mA.

I needed to calculate the voltage drop resistor. So I took incoming voltage of 12v - 1.7v= 10.3v.

10.3v / .02A = 515 ohm resistor. Right?

So I buy a 560 ohm resistor and wire it in series with my led. Luckily I am able to bench test with a variable power supply and a volt meter. As I bring the supply voltage up to 12v, the voltage at the led rises over the led 1.7 volts. Why?

What I ended up doing was wiring 2 - 560 ohm resistors in series and that brought the led voltage to where it needed to be. Why did Ohms law not work? What did I do wrong or not account for? Could the LED current be labeled wrong on the package?


texts: Interaction beween DMA transmission complete and peripheral interrupts

texts:
I have two related questions regarding using DMA with an STM32 chip.  I'm using STM32F031C6, but the answer should apply to other models.

I setup the USART to issue a character match interrupt.  I'm using DMA to read the characters from the USART.  I've noticed in practice that the matched character has already been copied to memory by the time the character match interrupt occurs.  Is this behaviour something that is reliable or is it a potential race condition? I didn't see this addressed in the reference manual.

I setup the A2D to read a sequence of channels and issue an end-of-sequence EOSEQ interrupt upon completion.  I'm using DMA to read the values into memory.  Is there any guarantee that the   value will have already been copied to memory at the point the EOSEQ happens?  I didn't see this addressed in the reference manual.


texts: Is it safe to adjust pot on sc-300 led driver by supernight

texts: Bought this the led driver (SC-300 by supernight) which claims to be a 12V 30A supply. I am drawing maybe 6 amps from it for what I'm testing. I noticed a pot on the side turning it changes the out put voltage. Any thoughts as to what this is for. Why allow the user to adjust output voltage if your only going to advertise it as a 12V supply? It seems to be able to output up to maybe 15V but. Ran it at 14 for a while doesn't appear to be getting too hot. Can I run it at higher voltages with out concern?


texts: Mysterious piece of metal shipped with a soldering iron

texts:
This piece of metal was packaged with my new soldering iron.

Does anybody know what is it ? Is it a stand ?


texts: WiFi antenna understanding, which is 2.4, 5 GHz

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My USB WiFi adapter has two antenna connectors, I have a lack of knowledge of these connectors, few questinos:

how to check which connector is 2.4/5 GHz or both are 2.4/5 GHz at the same time?
comes with these two antena, as I see its a 2.4 GHz antenna, then why vendor gives me two 2.4 GHz antennas without 5 GHz antenna?
I could connect to one connector 2.4 GHz antenna and to the second connector 5 GHz antenna?


texts:
I'm designing a PCB involving signals up to 6 GHz. I want to use through-hole SMA connectors like these:

If I route the RF traces on the top of the board, will the center contact of the through-hole connector sticking out to the other side of the board have any significant effects (compared to something like an edge mount connector)?

(I have been looking around for advice on this but have not really found anything, apart from USB 3.0 application notes suggesting that the superspeed traces better be routed on the opposite side of the board when using through-hole USB 3.0 connectors.)

In case my description is not clear I'd be happy to provide pictures to illustrate.

Thank you!

Update: I think I'm going to go with edge launch connectors, just to be safe. Thanks for the answers.


texts: Wiring confusion in joining two cables with 5.5 x 2.1 mm DC male ends, please explain

texts:
I've got a 12V powerbank that I would like to use with a 12v device. The power bank output and the device both require 5.5 x 2.1mm male plugs.

I've actually got some random cables and have found two of these exact cables. Now for the weird thing, when I test for continuity with a multimeter, it is different for these cables - so for one cable, I get continuity when I use the two outside surfaces of both the 5.5mm ends. However, on the other cable, I get continuity when I use the outside surface of one end and the inside surface of the other end. Does this not matter for a DC circuit? So if I randomly join together two cables with 5.5mm ends, then I don't need to worry how it is joined or should I make sure the continuity is inside part to inside part and outside with outside?


texts: ESP32 with JGY-371 stepper motor and L293D

texts:
I'm currently trying to make an automatic chicken coop door,
I plan to use an ESP32 with an L293D motor driver and JGY-371 geared motor 30RPM (shop link).

The door should not exceed 1kg and should pull a 30/40 centimeter distance.The torque needed by my system should be 0.5N.m if I calculated well it should fit with the motor specification
I am planning to connect ESP32, L293D and the stepper motor using the following schematic:

Since I'm more an embedded software engineer than electronic engineer, I want to be sure if I have sourced good parts for my project and if my schematic looks correct?


texts: Op-Amp and foldback limiting of voltage power supply

texts:
I am new in forum.

Can an opamp which drives a small load and whose output current exceeds the maximum output current of the opamp cause a foldback limiting of the power supply?

If I use a class ab push-pull stage to boost the output current and the current Ic for a voltage Vce does not respect the SOA (safe operating area) of the transistors, can I have also foldack limiting from the power supply?

I have been working on a circuit and every time I exceed a current amplitude level, I have a foldback limiting from the power supply.I verified and I don't have voltage saturation of my opamp and the input respect the common mode range input given in the datasheet.


texts: Altium Designer 15.1: "From-To"s are only displayed when moving component

texts:
I am having an issue in Altium Designer 15.1 where the "From-To"s are only shown when I'm moving the component. I prefer them to be visible all the time. I have gone into the layer stack dialog, clicked the Show/Hide tab, clicked "From To Settings", and ensured "Show From Tos" is set to "Automatic". I have also tried setting it to "Always", but they still do not appear. The connections are clearly still made, though, because when I hover over a pad in the net, all other pads in the same net are highlighted.

Are there any other settings that would hide "From-To"s, even when the display settings are set to "show"?


texts: How to test SMD bluetooth modules without soldering them to a board

texts:
I have made a costum PCB with components and a WT51822-S2 bluetooth module. After testing, there seems to be a low percentage of modules that have a fault in them. Since they are SMD modules, with connections on the sides, its hard to desolder them if faulty. They are soldered on easily with a normal solderin iron but desoldering, thats a whole other thing.

Is there a way to test SMD modules without actually soldering them on the pcb? I have tried pressing them on (with force and duck tape) but some pins have contact, others dont. I have also made a brakeout board for testing, but it still requiers soldering.

what to do?


texts: Circuit for Current Injection and Voltage Reading

texts:
I am developing a sensor based on the principle of EIT (Electrical Impedance Tomography).

For the project, I need to inject into the material I am using, a constant current between two electrodes placed at the periphery of the sensor and then
read the corresponding voltages at the other electrodes (I have 16 electrodes).
Then the current has to be switched between the remainig electrode pairs in a scanning cycle (as you can see in the picture-only 8 electrodes in the picture).

I am using 2 demultiplexer with 16 outputs to control the current injection. One multiplexer serves to control the current source and the other
one for the ground in order to switch all the electrodes between ground and current source.

The MUX are controlled by the digital outputs of a NI DAQ-6353 card which also serves for reading the voltages in a differential mode.(you can see it in the schematic)

The circuit is powered with 5V and the resistance of the sensor is around 60K Ohm.

I am using a 10uA constant current. The power source will be external, as my DAQ can only supply 5mA and I will need to change the current amplitude in the future.

My question is this: is the circuit going to work? I don't see any problem, I have also tested the constant current generator and it works up to a load of 100K, but maybe someone with a more expert eye could see if there are some errors.


texts: How to control 12 V with Arduino's 5 V pins?

texts: I'm trying to program a parallel EEPROM which requires Vpp high voltage cycle to write a byte. I want to control Vpp with an Arduino pin so I can write a byte onto an address in EEPROM. But I couldn't do it. In fact I tried to control Vpp with an NPN transistor but it burned up. How can I overcome this ? (I'm using Arduino Nano.)


texts:
I have an interesting project and I could use a little help. I'm using a microcontroller who's input to the ADC and output on the GPIO and DAC pins are all within a 3.3V range, and I have to interface with a 15V logic controller.

Can anyone tell me what would be the best way to convert down to 3.3V (assuming there's a better way than a resistive divider with a Zener to clamp) from 15V for the simple I/O?

How to scale down properly for the ADC and scale up properly for the DAC? At least, does anyone know of an industry standard or commonly used driver chip for this?


texts: How to interface with a bus that's powered when the rest of my circuit is off

texts:
I'm working on interfacing to a SPI bus that is exhibiting some... bad behavior.

The bus comes from a control box on a toy drumset. The control box is the SPI master, and it can be turned on and off with a built-in button. A separate circuit that reads from the drumpads is the only slave on the bus.

What I am doing is this: I have basically added a master to the bus, in the form of a microcontroller. I know that this isn't a standard use of SPI, but it is for a hobby project, so I don't care. The two masters never operate simultaneously, so there are no conflicts. I mostly enforce this: If the control box is on, I don't plug in the USB cable to the microcontroller (I'm using a Pro Micro). Also, if the microcontroller detects the control box is on, the uC will end SPI communications.

Here is my circuit. I still need to buffer the MISO line, but other than that it's what I'm using.

There are three states this circuit can be in:

Off - control box is off and the Pro Micro is unplugged
Control box power - The control box is on, but the Pro Micro is off, thanks to the Schottky diode. The control box is the master, and the Pro Micro is isolated from the circuit.
Pro Micro power - The USB cable is plugged in, and the Pro Micro is the master. The control box is off.

My issue occurs during state 1. Although the control box is off, the SPI lines coming out of it are showing 3.3V. For some reason, the control box powers MOSI, CLK, and CS even though its VCC shows 0V! When neither the control box nor Pro Micro is on, the buffer is unpowered, and the outputs are seeing 3.3V. Somehow this is reverse-powering the buffer, which in turn powers the rest of my circuit.

I'm using a  SN74AHC125 buffer.

Before I started using the buffer, I connected the SPI lines directly to my microcontroller (ATMega 32U4). I had the same problem: The SPI lines powered my Pro Micro through the reverse protection diodes on the pins.

So how can I drive these lines when they are still powered while the rest of my circuit is off?


texts: Differences in CMOS fan-out between the two logic level

texts:
I was taught that a number of inputs A CMOS gate can drive when it's output is low differs from the number of inputs it can drive when its output is high.
Is it because of different properties of the P channel and N channel MOSFETs, and if it's not the case, why is it, then?


texts: What is the purpose of RC components to ground in this class AB amplifier?

texts: I'm talking about R6/C4. It seems like it would be filtering of some kind as the C4 will have it's voltage at the highest for DC or low frequency input, but I don't really understand the purpose.


texts: Why propagation delay is measured at 50% of the input and output waveform?

texts: I didn't find the concept of propagation delay measured at a particular point on the waveform.


texts:
I've been trying to get a motor regen power dissipation circuit working that I pulled from here.  The circuit works as provided but when I attempt to modify the load resistor, the mosfet is not longer being switched at 10-12V, it generally falls down to 5V or so.  It appears that the BJT isn't being driven fully and thus the mosfet is not being driven fully.  I'm at a loss as to why this is the case, can anyone explain this?

Attached are the LTSpice simulation files.


texts: Can an ATmega or ATtiny device signature be read while running?

texts:
While programming an ATtiny or ATmega, avrdude prints the device signature, in this example it is an ATtiny.

avrdude: Device signature = 0x1e910a

Can I read this signature on a running device using C++ code (avr-gcc)?  For ATmega1280 there is a chapter 29.6.10 writing about it, but I'm a bit puzzled by how I can code it in C++.

I want to be able to make the device send its device ID back to the controlling PC, so the PC can make decisions on it.


texts: Here is my switch schematic and simulation,but when the control(red) is off,is't it the output(purple) be 0 whatever i(black) is 1 or 0?Is there any method can modify this error?


texts:
in my antennas book (I do not put its reference because it is not in english) it is written that, at high distance from the source, the electromagnetic field radiated by it is a spherical wave.

This can be shown by analyzing the expression of the EM field at high distance generated by some specific antennas. For instance, for a half-wave dipole (which is not the short herzian dipole) we get (Reference here, page 17):

It is a spherical wave because its dependence on r is given by the term:

\$\frac{e^{-jkr}}{r}\$

I do not understand how can be this physically possible. A spherical wave is ideally generated only from a point source. I easily understand how even the wave generated by a small source (for example a short Herzian dipole) can be, at high distance, approximated as spherical. But in this case, in which the linear current source is not short, I don't understand why the wave cannot be, more plausibly (from a physical point of view), cylindrical. Furthermore, if it is true that at a great distance any wave is spherical, in which situations do cylindrical waves exist? I can't imagine how a cylinder becomes a sphere at a great distance.


texts: How short is short enough for pulse measurement

texts:
I am doing pulse measurement to solve the self-heating problem.

I control the frequency and duty cycle.

I know that pulse width = duty cycle / (frequency *100).

I want to know what the boundary condition is.

In other words, I want to determine at what point I transition between isothermal and self-heating.

Does 2 % of duty cycle signal cause the 2 % of power dissipation?


texts:
Much of USA residential is split phase, 120V x 2 and neutral. It’s my understanding the phase difference is 180 degrees of time domain.  How are the split phase legs combine to equal 220V?

Related: Do water heaters, dryers or stoves just use half the legs in separate circuits operating at 120V or are the legs somehow combine?

Thank you


texts: Potting transformers for mechanical noise reduction

texts:
Potting some noisy transformers failed to reduce the sound. My question is where the problem might be.

The setup is a row of small (about 0.75x2x4 cm) transformers on a PCB as part of a power circuit. They are oriented so they lie flat and the core is parallel to the PCB. The unit is new.

I removed a plastic wrapper from around the coils, built a dam around each transformer, and filled with low-viscosity potting epoxy. The coils are completely encased by the epoxy but the outer frame is not.

I'm speculating that the coils were too tightly wound for the epoxy to get in, but I'm still surprised there was no noise reduction at all. It seems I misunderstand the mechanics of what is going on.

Edit: This is in a CCFL inverter circuit. I don't know the frequency, but I assume it is typical for this application. There is no sound when the CCFL are at full power, just when the lights are dimmed with PWM.


texts:
I needed a reasonably stable 6.2V power supply for my audio amplifier project. I've found a few AIC1563PN dc-dc converters (looks identical to MC34063 according to the datasheet) which I salvaged from some old modems and used one of them as a step-down converter.

I've connected it according to the datasheet with an extra LC-filter at the output to reduce rippling. The diode I've used is 1N5817. The circuit is powered from a non-regulated wall wart "9V 500mA" adapter that outputs around 14.5V with no load and drops to 14V when I connect it to the circuit with load. After measuring output voltage I had some strange results:

Vout = 4.45V with no load
Vout = 3.79V with 10k load
Vout = 2.38V with 620 Ohm load

Why is it performing so bad? According to my calculations, Vout is supposed to be around 6.2V and since the converter is capable of delivering relatively high current, there shouldn't be such a huge voltage drop. Or should I use a different (better-performing) converter for this task?

Update: I've just measured the resistance of R2 and.. it was only a few ohms. However the color code is "orange-white-red-gold". Weird. I've checked all the components, but I never thought that something like a 3.9k resistor could malfunction. Wasted many hours because of that resistor :) Anyway, thank you everyone for your effort and patience, it was a silly mistake after all.


texts:
I have doubt about beta of feedback loop of inverting amplifier.

The expression for the feedback gain is :

$$A_{cl} =\frac{A}{1 + A \cdot \beta}$$

what is value of beta here? and how do I reach to final expression

$$A_{cl} =\frac{R_f}{R_in}$$


texts: What is a good alternative for the UA741 opamp in hobby projects?

texts:
Related to What's the uA741's appeal?, a lot of schematics use this rather dated opamp. My follow-up question would be: What is a good alternative?

Of course if you have specific requirements you just search for the correct part. What I'm talking about is, what should be the default opamp I stock in my parts bin?

Imagine the average hobby project with a breadboard and an Arduino, single-supply, probably 5V, frequencies in the audio spectrum, and accidental shorts.

It should just be a nice, single-ended, well behaved (no phase reversal) opamp with a large voltage swing (preferably rail-to-rail), and reasonable performance for audio.

Some comments on the linked question mention LM358 and LM324, but I've read the low slew-rate may be bad for audio, which is what most of my analogue signals are.


texts: What technique/sensor can I use to recognized tagged objects thrown onto a surface?

texts:
I am trying to implement a concept for somebody else.

Basically, I want to create a smart surface. I want to create a surface I can throw one or more tagged objects on that should all be recognized.

I am unsure how to this and what sensors I should use. I have been thinking about using one of the NFC ICs from NXP. However, designing a circuit board and buying this IC is too expensive for our idea. I'm also unsure of whether the surface area will cause problems, because it'll be quite large (think of a small coffee table).

I've also been thinking about other ways to recognize objects, but I have not come up with anything yet. I am probably not using the correct term.

Does anyone know of a type or sensor or technique to implement this?

Note: I am a computer engineer, not an electrical engineer. I know the basics, but really not much more than that, so I prefer a solution that is available as a simple IC or a complete circuit board with the really complicated things done for me by the experts :)


texts:
Pretty basic requirements:

two PWM signals (PWM1, PWM2)
20 individual LEDs sitting behind 20 different symbols (as backlight)
normally, when on standby, backlight is 'dim' (PWM1) for all LEDs
when a particular symbol/s needs to be activated, backlight turns 'bright' (PWM2)
there are 20 outputs from MCU for these 20 LEDs.

what's the most cost effective or efficient approach?


texts:
This is the full schematic of the circuit

theremin http://img443.imageshack.us/img443/9292/fulltheremin.png

Full size: http://img443.imageshack.us/img443/9292/fulltheremin.png

It didn't work on the first try.

A theremin is an electric instrument which emit a constant note and you can change it's tone (frequency) and volume (amplitude) with your hands and a pair of antennas.

On this schematic we have a theremin which only varies its frequency.
There's 3 transistors, on the sides two BC546 (I'm using BC547B that have more hFE) that are working as oscillators each with its own tank circuit consisting on an 100uH inductor (L1/L2) and two capacitors of 27pF (C4/C13) and 15pF (C5/C14) on parallel.
Either oscillator on both sides are the same and are quite responsive on frequency if I get my hands near them but, the left one has a 4.7K potentiometer (R10) on series with the 15pF capacitor to vary the base oscillation frequency and the right one should have an antenna connected to its transistor collector through a 15pF capacitor (C16), making it more responsive.

The output of both oscillators (OSC1 & OSC2) are fed to the output stage on the middle through 1M resistors (R8-R9) using direct coupling. This should sum them up in one signal and rise the impedance of the output signal.

The main problem is, on Q1 base, where the signals meet, there's no signal.

If I disconnect each oscillator, on OSC1 and OSC2 I get a healthy output of approximately 8Vpp 1~20KHz with an offset of ~10V with a new 9V battery.

For testing purposes I disassembled everything and reassemble only the left oscillator.

My mission: be able to make its output signal usable.

Using a 10nF decoupling capacitor on OSC1 I'm trying to buffer this output to get a stable audio signal without success.

I've tried a simple voltage follower with an LM358 Op-Amp but the signal won't show on the output.

I noticed while trying to offset the signal to Vcc/2 to feed it to my Op-Amp is that a 4.7K+4.7K voltage divider will drop down the signal to 0V just on the decoupled side of the capacitor, but with a 1M+1M voltage divider the signal will be kept healthy. So I guess it's an input impedance problem on the buffer side.

So I went with a common collector voltage follower with a second BC547B (collector to Vcc and a 1M resistor between emitter and ground, feeding the signal to its base), and I did get some but minimal and unusable output at the emitter. Before the output decoupling capacitor (emitter) on this voltage follower I got the offset-ed signal near Vcc, so I guessed the transistor was getting saturated by the high voltage signal.

Then I tried to divide the input signal by an order of magnitude with a 1M+100K divider before feeding it to the base, but the signal will be lost right after the decoupling capacitor on OSC1, just like it happened with the op-amp.

What should I try next?

I guess is obvious that I need a high impedance voltage follower but get a lower input signal too. But when I try to divide it before feeding to the buffer it will drop down to zero.


texts: If I have an IC, any IC, with a V+ and a V- that has a minimum voltage requirement of 3V to operate. Say I supply that exact 3V, but I want to add a silicon diode to the V- to prevent a reverse voltage from damaging the IC. Would it mean that I now have to compensate my voltage supply to accommodate the 3V drop and the 0.7V drop? Or would the diode have no effect to my circuit?


texts: Mosfet provokes high voltage drop and become hot

texts:
I'm using a STP16NF06L mosfet to drive a pump (12V / 3A). The problem is: there is only 5V at the pump (so 7V voltage drop at the mosfet), and because of that the mosfet becomes instantly hot.
I'm driving the mosfet with the raspberry pi through an optocoupler.

simulate this circuit – Schematic created using CircuitLab

I have measured 5V between mosfet gate and ground, I think it should be fully on.


texts: Why the Inrush current increase with decreasing voltage?

texts:
Here are the voltage and current shown for the primary winding of a transformer or an ideal inductor when the voltage is sinusodial.

My question is why the current is increasing when the voltage is decreasing as shown in the black box ? Its obvious that current should be increasing with increasing voltage and current should be decreasing with decreasing voltage but here the current is increasing for decreasing voltage.

And the current decreases during the negative voltage cycles only.

What is the the reason behind all this ?


texts: Adafruit audio FX mini and 2.5W amplifier

texts:
I am connecting Adafruit's Audio FX Mini board to a small Adafruit's amplifier. In order to save some power when the sound board is not outputting any sound, I wanted to connect ACT pin of the sound board with SD (shutdown) pin of the amp (PDF).

But if I connect directly these two pins, I seem to get completely opposite result, the background buzz (which is also normally heard) is heard when the sound is not played, and the sound goes off completely when the board is playing something.

Am I missing something? Should I invert ACT? How?


texts: I am looking into buying a variac from Ebay, but many of the devices on sale are rated for 2 - 3kVA (@220VAC). Now my concern with these devices is that simply turning them on (with or without load) will cause a power huge surge that may blow my home's fuse. Is there a rule of thumb for maximum input current at initial power on?


texts: How to find the switching threshold of CMOS inverter from it's transfer characteristics in Cadence Virtuoso?


texts: What is the use of NRST pin in STM32F401RCT6?

texts:
What is the use of the NRST pin in STM32F401RTC microcontroller. I am using the SWD interface to program and debug flash memory of the controller. I am finding NRST pins in both microcontroller as well as stlink debugger.

I am confused, what is the use of NRST pins? Is it used to reset the program which we flash and allow us to program it again? And why is a capacitor connected on the outer side of the pin and to ground?

What is the use of it in microcontroller and Stlink? How does it work?

I checked in Google. The explanation given was too technical, so kindly explain to me in simple terms.


texts: I have a direct mapped cache of size S with the line size L. The cache is physically indexed and tagged. The physical address is 50 bits, numbered from 0 to 49 (with 0 being the least significant bit). The machine has a word size of 4 bits and the memory is byte-addressable. Which bits of the 50 bits are compared with the address tag?


texts: I already have a 4 channel oscilloscope but it's quite old and I might have some money soon to upgrade with. The price for a 4 channel is almost 2-3x that of a 2 channel, but is the cost justified by the increased utility? I find I mostly use 2 channels on my scope currently, occasionally using a third but so far no use for all four. I'm dealing with serial protocols and video signals most of the time.


texts:
I am trying to solve a few example questions relating to input voltage and input noise for the following questions.

and

I understand that I need to calculate the maximum noise voltage acceptable for the required SNR using the equation, SNR = 20log(Signal/Noise).

The thing I am having trouble understanding is for the first question, in the solutions the input noise voltage is calculated using:

Whilst in the solution for the second problem it uses:

I cannot see any difference in the question as to why one would be squared and the other not. Thanks in advance.


texts:
I am using a PIC18F4620 and an XC8 compiler. I am trying to create a file and send it to the SD card. I am using the MDD library from the MLA Legacy. My main is:

FSFILE * file;
char sendBuffer[22] = "This is test string 1";

//**************************************************
// main function
//**************************************************
int main()
{
    initIO();
    PORTBbits.RB0 = 0;
    while(1)
    {
        // Initialise SPI and SD-card
        while ( !MDD_MediaDetect() )
            ;

        MDD_SDSPI_InitIO();

        MDD_SDSPI_MediaInitialize();

        // Initialize the library
        while ( !FSInit() )
            ;

    #ifdef ALLOW_WRITES

        // Create a new file
        file = FSfopenpgm ( "FILE.TXT", "w" );
        if ( file == NULL )
            while(1);

        // Write 21 1-byte objects from sendBuffer into the file
            if ( FSfwrite ( (void *) sendBuffer, 1, 21, file ) != 21 )
                    while(1);

        // Close the file
            if ( FSfclose ( file ) )
                    while(1);

    #endif

    MDD_SDSPI_SectorWrite(TAG_SECTOR_START, file, FALSE);

    //    Delay10KTCYx(100000000);

    PORTBbits.RB0 = 1;         //LED
    }
    return (0);
}

Does the code look OK? I am not sure about the MDD_SDSPI_SectorWrite function, and I don't know how to find the address of the sector in which I want to write the file. I know the error handling is bad. I will change it eventually.


texts: Are flags strictly related to interrupts or not?

texts:
If we want to some flag to be set when true (for example FIFO is full), does that mean that we have to enable the interrupts?

Whether it will be set if interrupts are not enabled?

Are that flags always triggered, but it is on us to chose the way how we want to handle those events (polling or interrupt way)?


texts:
The core problem I am having is that I need to be able to control a DC to DC voltage regulator based on input from a 4 to 20 mA signal. The end goal is to have the output voltage of this regulator be able to dynamically change based on this input current signal (Output up to 24 VDC). The voltage source supplying the regulator is 24 VDC also.

I want to be able to control a 10K potentiometer in the regulator using the signal form the 4 to 20 mA current loop. I have been unable to find a device or circuit that can accomplish this task.

I would appreciate any suggestions or assistance anyone could offer. I might be missing a much simpler to the problem then what i am currently trying.
Thanks.

P.S. This is my first post on the forums.


texts:
I have a PC with a 280 W PSU.

I am thinking about buying an inverter but I am confused.

I have an inverter which requires 36 VDC. Will it work if I add 3 12 V, 50 Ah batteries in series? Or shall I buy a new 12 V unit, with a 12 V, 100 Ah battery?

Also if I use 3 car batteries instead, will it make any difference?


texts: How can 16 buttons be connected with only 8 wires?

texts:
Here is the product. I understand the idea: these 16 buttons use a 4x4 matrix. 4 lines for rows, 4 lines for columns, and we have 8 cables.

But:

How can this work without any multiplexer ?
Can this detect accurately presses of multiple buttons? Even if buttons use same row or same column? Example: buttons at position (2,2) (2,3), (3,2), and (3,3) pressed at the same time.
How does it work?


texts: How to reduce spike in Power Supply and GND (SCR + Ignition Coil)

texts:
My circuit:

Signal coupled in power supply (3.3V) of STM32F103 during spark:

Is there any benefit to using this diode (circled in red) or not (without this diode the snubber circuit will start working)?

What is  a better solution/topology to avoid noise and maintain the spark efficiency?

My doubt is:

If I use this shown configuration, is it more difficult to cut-off the SCR (maintain hold current for a long period) and can it disturb another part in circuit?

I use an automotive sparkplug resistive cable with 4K ohms and a earth strap to connect the engine with ignition coil GND (frame).

The diode D4 is relevant during the C3 charging, is it a necessary solution or does it not make a big difference in this circuit?


texts: Reading a gas sensor with range from 0 to 60mV with an ADC

texts:
I need to take a reading using an ATmega328P of a gas sensor. The ATmega328p has a built in 10bit ADC giving only 1024 'steps'

The data sheets for my O2 sensor are:
http://www.citytech.com/PDF-Datasheets/ao2.pdf
http://www.quantika.ro/prospecte/ao2.pdf

It works by generating a voltage by chemical reaction to O2. It requires a load resistor of 10K to 'get it going'

The T90 or T99 is the time in seconds a sensor takes to reach n% of the correct reading.

I was wondering for the range 0-100% gas reading, the sensor gives 0-60mV.

What would be the best solution to give me a 0.01 resolution?

10000 steps would mean a 14bit ADC? Peferably I2C or SPI so something like the ADS1118? Do I need to use an OpAmp to amplify the signal first? Is there an instrumentation amplifier with a built in PGA that will suit this application?

I was able to put a 10k Resistor in parallel with the sensor, using an ADS1115 ADC I was able to read the value using i2c with my ATmega328p. The ADS1115 (had to remove link as reputation not good enough) was good but I found the PGA gain not enough for me.

If I use the powered version on this o2 sensor called a mox20 (had to remove link as reputation not good enough but google mox-20 oxygen sensor) as the output is much higher, I don't need so much amplification but this sensor is more expensive so I am looking for a circuit idea maybe using an op-amp and another ADC or ideally an ADC with a built in PGA with the gain I would require.


texts: Can I apply a 24v DC current to an analog voltmeter graduated between 8 and 16v for a few seconds?

texts:
I have an analog voltmeter that is used to monitor 12V batteries, with a needle going between 8V and 16V)

In a specific situation, I have a series/parallel switch which turns two of my batteries into a 24V battery, and I want to make sure that this complicated switch is indeed working (notably, it won't set if there's not enough current in the batteries, which happened to me once in the past).
In other words, I don't care whether I have 24V or 26V there, I just want to make sure that I have, say more than 15V.

I can think of many ways to achieve this, but since I already have a voltmeter with all the cabling in place, it would make sense to use this if at all possible. Of course this would just be very intermittent.

Will the needle go through the roof, or would my voltmeter die a painful death ?

Unfortunately, I can't easily access the rating information of the voltmeter.


texts: AC servo ASDA-B2 modbus position control

texts:
I have a very specific question on ASDA-B2 servo driver and I hope there is someone who has hands on experience with it who can help me out.

I have referred to this user manual and it is not very clear on position control. In Chapter 6 it describes the modes of operation. The P mode (External Position Control mode) description says that the position control is achieved using an external pulse command. Topic 6.2 describes this further.

I want the motor to be controlled using modbus via RS485 serial communication (so that I can directly control the motor by a PC). Does this mean I have to use an external pulse generator circuitry connected to the controller if I need position controlling?


texts: How does this BJT transistor circuit works?

texts:
I just wanted to know a little more about this circuit about how it works a more in depth analysis I mean. I know there's some kind of differential amplifier and a Zener diode for voltage regulation connected to a voltage divider. (correct me if I'm wrong).

And I can not get any voltage from Vo in Proteus 8 simulation what's wrong? ( the simulation file)


texts: I'm using FreeRTOS generated with the help of CubeMX. Everything was working fine until I added USB CDC unit. When I used CDC_Transmit_FS() before starting kernel, I could receive data over USB. However, when I paste the same code to thread, this is not working.


texts: Mystery circuit: latching relay control with transitor / capacitor - why doesn't it work?

texts:
I've been looking for a way to control a latching relay with a microcontroller that doesn't quite have enough current on the output pins to operate it directly. I found this intriguing circuit using a 220uF capacitor and an NPN transistor, but haven't had any luck getting it to work as described.

The circuit I'm referring to is the first one on this page, labeled "Pulse Latching Relay On/Off":

Transistor Circuits: Latching Relay

Here it is below:

simulate this circuit – Schematic created using CircuitLab

From the circuit description:

  The circuit above produces a strong pulse to latch the relay ON and the input voltage must remain HIGH. The 220u gradually charges and the current falls to a very low level. When the input voltage is removed, the circuit produces a pulse in the opposite direction to unlatch the relay.

Problem is, the circuit doesn't work. They don't clearly label the inputs, but I gather that top is (+) and bottom is (-), and the 10K operates as a pullup, holding the transistor open to discharge the capacitor. When the lower input is connected to ground, the transistor switches off, and here's where I get confused. Is there supposed to be electron flow from base to emitter to charge the capacitor via the coil? Seems that would reverse-biase the BE junction and current wouldn't flow.

My attempts to breadboard this with a T2n3904 and a 470uF electrolytic have failed.

Is this circuit bogus or am I just stupid?


texts: How can I find out the actual rpms my dc motor at any given moment?

texts: In my next project it will be very helpful to monitor the speed of my dc motor. How can I accomplish this?


texts: Can anyone tell me any exclusive application of Johnson counter?

texts: I went through many types of counter in my digital electronics text book. Each one was interesting. When I came across Johnson counter, I was not able to figure out any practical application. Can anyone help me for the same?


texts:
I'm trying to build a diving flashlight and now I'm stuck with the electrical part.

I have a \$12\$V \$10\$W high brightness LED, and am now trying to decide which is the best option for the batteries. For now, I guess the best choice is a pack of \$18650\; \left(3.7\; V\right)\$.
Found a package with \$10\$ batteries with nominal capacity* of \$4200\$ mAh for $\$15\$.

So, the plan is to put \$3\$ groups of \$3\$ batteries in series. This way, it should provide \$\left(3\times4.2\right)=12.6\;\$V at full charge* and \$\left(3*2.7\right)=8.1\;\$V at minimum charge*, and a nominal \$\left(3\times 4200\right)=12600\;\$mAh of capacity*.

To maintain the brightness of the LED constant, is there an easy way to build a regulator with input \$8 \sim13\$V and output \$12\;\$V without losing much power? Or another better idea?

UPDATE

I don't have so much skill about electronics, and don't know exactly how to find the correct datasheet, but the LED is this:

*: Edited and replaced with correct terms


texts: How can the SI unit of resistivity [Ωm] be interpreted?

texts:
The way I interpret the resistance \$R\$ of a resistor, which has dimensions \$ [\frac{\mathrm{V}}{\mathrm{A}}] \$ is: how many volts must be applied across the resistor to achieve 1 ampere of current?

The conductance \$G\$, which has dimensions \$ [\frac{\mathrm{A}}{\mathrm{V}}] \$ is then: how many amperes of current flow through the resistor when applying 1 volt?

I realize that these quantities are related to the geometry, whereas the resistivity \$ \rho = R\times \frac{A}{L} \$ which has dimensions \$ [\Omega \cdot \mathrm{m}] \$ is an intrinsic property of the material (doping of semi-conductor, electron/hole mobility, etc).

However, I cannot achieve an intuitive understanding to interpret the dimensions of resistivity. Can this be clarified?


texts:
I recently bought a 3G SIM5320A Shield Click here.I'm facing some problems while communicating with the module using a USB to serial converter.The module doesn't seem to respond to the AT commands. I tried  different settings for the COM port such as changing the baud rate but still no luck.Any suggestions on what might be wrong.
Note: I'm powering the module from the USB to serial converter.

I tried Arduino mega to send AT commands by uploading an example sketch from the adafruit_fona library still doesn't work.FONA basic test
Initializing....(May take 3 seconds)
Attempting to open comm with ATs
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
Timeout: No response to AT... last ditch attempt.
    ---> AT
    <---
    ---> AT
    <---
    ---> AT
    <---
    ---> ATE0
    <---
    ---> ATE0
    <---
Couldn't find FONA

I got this working the issue seems to be the supply has to be above 9volts.Now the module is easily drawing 178mA standby.


texts:
I have an infrared LED that needs a voltage drop of ~1.55V as well as a BJT to sink the current when the LED is in operation. That give me a total voltage drop needed of ~2.2V and unfortunately I have only got a 2V supply.
I have been told that there is such thing as capacitor stacking and it essentially charges two capacitors in parallel to the supply voltage (2V) and then discharges them in series which gives it twice the potential. However, firstly I am not even sure if that statement is correct, and secondly I wanted someone to explain to me how this actually happens?
I have a circuit diagram that I believe to do the correct thing but still am not sure as to what is going on with it:

simulate this circuit – Schematic created using CircuitLab

So the way I understand it, given enough time, the capictors will charge to full capacity (2V) and then once the discharge trigger is made high cause a current to be present at the base of the PNP (Q1)  and this will allow current to flow through that transistor.
I don't understand how both can discharge to make twice the voltage... Any help in clarifying this with possible help from a diagram would be great.


texts: USB connector to BNC connectors back to USB connector

texts: I would like to split a USB cable (carrying data from an instrument) up into separate parts, I think there are 4 or 5 connectors inside of it including ground, then send two each through my BNC ports. I have several BNC ports into an apparatus which is hermetically sealed. Would it be a bad idea to do this? I've heard something about possible problems with impedance, but I don't know enough to say if this is a bad idea or not.


texts: Potentiometer not changing voltage reading

texts:
I'm rather new to the electrical space and Im starting out by trying to complete basic circuits in order to make sure I understand how all of the components work.  After completing some basic labs with a 5v power source, an LED, and some resistors I decided to try replacing the resistors with a potentiometer.  It's my understanding that by using terminals 1 and 2, you can turn the pot into a rheostat or adjustable resistor.  So I put the pot in place of the resistor and sure enough, I could make the LED dim and brighten by adjusting the position of the knob on the pot.  I also hooked up my multimeter in parallel to the LED and saw the voltage increase and decrease with the LED.  This all made sense to me and was how I thought things should work.  However, I then unplugged the LED from the breadboard just leaving the multimeter leads attached to the circuit.  The reading returned immediately to 5v and stayed there regardless of where the pot was set.  So now Im a little confused.  Why would my multimeter only register a change in voltage when the LED was in parallel?  Shouldnt the multimeter still be registering the changes in voltage based on where the pot is set?

I've found that if I configure the pot using all 3 terminals then it works as expected and I see the voltage changing on the multimeter even without the LED.  In that configuration Im using terminal 1 as ground, 2 as output, and 3 as input.  Im still confused why the initial experiment with using the pot as a rheostat with only two terminals wont register voltage change on my multimeter though.


texts: Simulating (transient) intermodulation distortion

texts:
I'm designing an audio amplifier and I'm trying to simulate and measure all the characteristic features of it (output power, offset, bandwidth, input/output impedances, etc.).

However, I don't know how to measure intermodulation distortion (IMD) or transient intermodulation distortion (TIM).

For IMD, I've read that one should put two generators of 19 kHz and 20 kHz in series at the input, and then measure the distortion at the output. However, I believe that for IMD, one should not take into account the harmonic distortion caused by these two signals (i.e. one shouldn't interpret the appearance of 38 kHz or 40 kHz at the output as IMD, because it is THD actually). So, how can one measure IMD in LTspice then?

Apart from that, I want to simulate the TIM. But, in this case, I don't even know how to perform this measurement. Is there a way to do it?


texts: NTC Thermistor Resistance Calculation for circuit using Wheatstone bridge, Op Amp & Arduino

texts:
I'm trying to work out the formula for thermistor resistance when using Wheatstone bridge/op amp circuit as opposed to a voltage divider circuit.  I know for a voltage divider the \$R_t\$ value is calculated as follows:

voltage output:

$$V_o = \frac{R_t}{R_t + R} \times Vcc$$

ADC value = \$V_i \times \frac{1023}{Vcc}\$

As \$V_o = V_i\$, these 2 formulae can be combined to give:

ADC value = \$\frac{R_t}{R_t + R} \times 1023\$
and ultimately:

$$R_t = \frac{R}{1023/ADC - 1}$$

For my circuit..

\$V_o = (\dfrac{R_t}{R_t + R_3} - \dfrac{R_2}{R_2 + R_1}) \times Vcc \times 10 \$ [Gain of 10]

I've combined this with \$V_i \times 1023 / Vcc \$ which gives:

$$ADC = (\dfrac{R_t}{R_t + R_3} - \dfrac{R_2}{R_2 + R_1}) \times 10 \times 1023 $$

Rearranging the ADC formula to isolate Rt I came up with:

$$ADC = (\dfrac{R_t}{R_t + R_3} - \dfrac{R_2}{R_2 + R_1}) \times 10 \times 1023 $$

With a lot of help I've come up with:

$$(\dfrac{R_t}{R_t + R_3}) = (\dfrac{ADC}{10230} + \dfrac{R_2}{R_1 + R_2})$$

$$1 + \dfrac{R_3}{R_t} = \dfrac{1}{\dfrac{ADC}{10230} + \dfrac{R_2}{R_1 + R2}}$$

$$1 + \dfrac{R_3}{R_t} = \dfrac{10230(R_1+R_2)}{ADC(R_1+R_2) + 10230 R_2}$$

$$\dfrac{R_3}{R_t} = \dfrac{10230(R_1+R_2)}{ADC(R_1+R_2) + 10230 R_2}-\dfrac{ADC(R_1+R_2) + 10230 R_2}{ADC(R_1+R_2) + 10230 R_2}$$

$$\dfrac{R_3}{R_t}=\dfrac{10230(R_1+R_2)-ADC(R_1+R_2)-10230R_2}{ADC(R_1+R_2) + 10230 R_2}$$

$$R_t[10230(R_1 + R_2) - ADC(R_1 + R_2) - 10230R_2] = R_3[ADC(R_1 + R_2) + 10230R_2]$$

$$R_t = \dfrac{R_3[ADC(R_1 + R_2) + 10230R_2]}{10230(R_1 + R_2) - ADC(R_1 + R_2) - 10230R_2}$$

$$R_t = \dfrac{R_3[ADC(R_1 + R_2) + 10230R_2]}{10230 R_1 - ADC(R_1 + R_2)}$$

I don't have the actual circuit schematic to hand at the moment but, apart from the wheatstone resistors and op amp leg & feedback resistor values, it looks like this:


texts:
This code if compiled has an error appear with (k) symbol. I need to implement this simple block. k (that represents the amount of delay) will come to my block from the previous block.

library ieee;
use ieee.std_logic_1164.all;
entity delay is
port( in_delay : in std_logic ;
       k : time ;
      out_delay : out std_logic);

end delay;
architecture behave of delay is

begin
  process (in_delay )
   begin
   out_delay <= in_delay  after k ns;
  end process ;
end behave;


texts:
I wolud like to use simple oneline code snippet for generating single clock cycle positive pulse

pulse <= '1', '0' after CLK_PERIOD;

However, it is not working (in ghdl simulator at least) is there any chance to improve it? Below, example of tb which only detects first pulse:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity tb is
end entity;

architecture bench of tb is

    signal clk : std_logic := '0';
    signal pulse : std_logic := '0';
    signal cnt : natural := 0;
    constant CLK_PERIOD : time := 10 ns;

begin

    main: process
    begin
        wait until rising_edge(clk);
        pulse <= '1';
        wait until rising_edge(clk);
        pulse <= '0';

        -- oneline pulse generation
        wait until rising_edge(clk);
        pulse <= '1', '0' after CLK_PERIOD;

        wait for 20 ns;
    wait;
    end process;

    count: process
    begin
        wait until rising_edge(clk) and pulse = '1';
        cnt <= cnt +1;
        report "pulse detected";
    end process;

    clk <= not clk after CLK_PERIOD / 2;

    end bench;

I don't understand why the second pulse is printed in gtkwave, while not detected by statement wait until rising_edge(clk) and pulse = '1'


texts: How exactly do USB audio interfaces interface with a computer? (specifically ADC)

texts:
I have seen the likes of M-Audio fast track and similar devices that somehow covert an analogue voltage audio signal to a digital data stream which you can connect via USB to your computer. If I open something like Garageband it just appears as another input without any special configuration. I am interested in building my own.

An example application would be; record guitar onto a computer software e.g. Garageband, Logic Pro etc.

I understand that there is a ADC (Analogue to Digital Converter) which will convert the analogue audio levels to digital.

What I am trying to figure out is, how does this interface with the computer?

All of these devices seem to work without needing specific drivers and such so, there I'm guessing there may be a specific protocol they all follow? I can't seem to find something exact.

If there is a protocol that they follow, does anyone have any info or any idea about this? Is this the same universal protocol that is used by the likes of USB audio speakers etc? Is this similar to SPDIF and the like? Is this conversion from output of ADC to USB data stream something which we can do, say, with a microcontroller?

I know that its much easier just to build an analogue preamp or the like to connect it to the audio input port on a PC but as I said, I am interested in how they make the USB interface.


texts:
I apologize for the stupid question, but I am a beginner in the analysis of BJT circuits. The Emitter-Base Junction of a npn BJT is forwand biased if the emitter current is positive?

Thank you for your help.


texts: Hardware based magnitude for accelerometer

texts:
In the past I've taken the magnitude of an accelerometer digitally, using the following equation:

magnitude = sqrt(x^2 + y^2 + z^2)

However, in order to do this I need to sample all three accelerometer planes (x, y, and z) which takes up three channels in my DAQ. This is fine for a single accelerometer, but now that I'm starting to use multiple accelerometer this means I need a lot of channels!

Seeing as I'm just taking the magnitude anyway, I was wondering how I would perform the same calculation in hardware, prior to sampling the planes, so that I only have to sample one channel per accelerometer as opposed to three.

Would someone be able to show me what the circuitry would look like for me to perform this magnitude calculation?

Thanks in advance.


texts: Thermistor Steinhart-Hart coefficient ABC

texts:
I am wondering how to find the Steinhart-Hart coefficients for the thermistor model
RL0503-5820-97-MS, and was given this data sheet. Where do I find these?


texts: Cortex M3 (ATSAM3N4B) Peripheral DMA read from SRAM ok, FLASH fails

texts:
I've stumbled across a peculiar problem with my PDC (Peripheral DMA Controller) where using the PDC to transfer a constant string from flash over UART 0 seems to produce an unexpected result. The correct number of bytes is sent but they are all zero.

The string is defined in the global namespace as follows

char* str = "Hello world!";

I only send it once at the start of main like this:

UART0->UART_TPR = str;               // PDC transfer pointer
UART0->UART_TCR = strlen(str);       // PDC counter
UART0->UART_PTCR = UART_PTCR_TXTEN;  // PDC enable for UART 0

which sends me 12 zeroes over UART on startup.

Now, if I copy the string into an array that is in function scope:

int main()
{
    // ... some initialization stuff ...
    char buffer[100];
    int i;

    for (i = 0; i < 100 && str[i] != '\0'; ++i)
    {
        buffer[i] = str[i];
    }
    buffer[i] = '\0';

    UART0->UART_TPR = buffer;               // PDC transfer pointer
    UART0->UART_TCR = strlen(buffer);       // PDC counter
    UART0->UART_PTCR = UART_PTCR_TXTEN;     // PDC enable for UART 0

    // ... other code here ...
}

This one sends me the string "Hello world!" over UART + one random character which is easy enough to fix.

My question is, why did the first method not work?

The datasheet states that the PDC can access any of the on-chip memories, so what is going on with Flash?

Using SAM-ICE I've confirmed the obvious:

The global variable's address starts with 0x004..., meaning that it resides in Flash
The local buffer address starts with 0x200..., menaning that it resides in SRAM.

This problem is happening on a commercial prototype board. I do have a SAM3N4C evaluation kit board that I can rewrite the code for if you require it in order to help me but I would like to avoid that if possible.

The datasheet sections that are of interest are the following:

Section 10.5 : ARM Cortex M3 -> Memory model (10.5.2 and 10.5.3 in particular)

Section 22 : Peripheral DMA Controller

Section 29 : UART (if it is not enough information look at 30, USART, it might give some clues).

I'm not sure what to think since I'm only accessing bytes so endian-ness and alignment shouldn't be a problem. Also, the flash section in the datasheet also says that the Flash can be read in bytes so I don't see a problem. Hence, I'm turning to the community for help. Thanks in advance.


texts: Does a plugged in 12v usb-charger use energy when no device is connected?

texts:
I hard-wired a 12v cigarette-plug into my a-pillar.

The whole point is to have an additional phone charger on the leftside where my phone mostly sits.

I connected it directly to the battery ( with a fuse ), so I can use it when the engine is off aswell.

When I connected the usb-charger to the cigarette-12v-plug an indicator-light came on. ( nothing else is connected ).

So obviously this is using power.

Will this drain my battery?
Do 12V usb-charger without an inidicator light use power when nothing else is connected?
if #2 is negative, how can i solve this?


texts: I'm attempting to build an Arduino-based device that will use NFC to know when my phone is close to it. My phone is a Nexus S, equipped with NFC. I'm looking for what I believe is called an NFC Transceiver, to be able to pair with my phone via NFC. I've found plenty of technical documents on this component, but can't seem to find anywhere that the general public can buy them in small quantities (namely 1 to 5).


texts: How to generate 6 phase shifted (60 degrees between each) PWM Signals?

texts:
Hi need to generate 6 phase shifted 5V PWM singnals. I need to take fitting microntroler (now it is PIC18F66K22 I'm looking for easiest to make). I want to know what step i will should take to success. If i good thinking after looking into datasheet will have 6, 8-bit timers. So i need to figure out how to creat phase shifting this PWM outputs for 1/6 period +dead band between each other.
I apologize for previouse  not so good question


texts: Using 16 x 4 Alphanumeric LCD with MikroC Pro for PIC compiler

texts:
I am trying to interface a 16x4 LCD to a PIC16F877 MCU. The project is just a digital clock showing date and time from a DS1307 RTC.

The display works correctly when I use a 16x2 LCD. But if I try to print the same thing, same code in the 16x4 LCD's 3rd and 4th row, the display prints it at 4rd column instead of 1. I have displayed the working and the not working screenshots below.

Maybe it is because of using 4-bit interface instead of 8. Or maybe some other issue. Can you please guide me:

I am using MikroC Pro for PIC compiler's library LCD display. It is a 4 bit interfacing library.

Schematic:

1st 2nd row:

3rd 4th row:

Code:

// LCD module connections
sbit LCD_RS at RB2_bit;
sbit LCD_EN at RB3_bit;
sbit LCD_D4 at RB4_bit;
sbit LCD_D5 at RB5_bit;
sbit LCD_D6 at RB6_bit;
sbit LCD_D7 at RB7_bit;

sbit LCD_RS_Direction at TRISB2_bit;
sbit LCD_EN_Direction at TRISB3_bit;
sbit LCD_D4_Direction at TRISB4_bit;
sbit LCD_D5_Direction at TRISB5_bit;
sbit LCD_D6_Direction at TRISB6_bit;
sbit LCD_D7_Direction at TRISB7_bit;
// End LCD module connections

unsigned short read_ds1307(unsigned short address)
{
  unsigned short r_data;
  I2C1_Start();
  I2C1_Wr(0xD0); //address 0x68 followed by direction bit (0 for write, 1 for read) 0x68 followed by 0 --> 0xD0
  I2C1_Wr(address);
  I2C1_Repeated_Start();
  I2C1_Wr(0xD1); //0x68 followed by 1 --> 0xD1
  r_data=I2C1_Rd(0);
  I2C1_Stop();
  return(r_data);
}

void write_ds1307(unsigned short address,unsigned short w_data)
{
  I2C1_Start(); // issue I2C start signal
  //address 0x68 followed by direction bit (0 for write, 1 for read) 0x68 followed by 0 --> 0xD0
  I2C1_Wr(0xD0); // send byte via I2C (device address + W)
  I2C1_Wr(address); // send byte (address of DS1307 location)
  I2C1_Wr(w_data); // send data (data to be written)
  I2C1_Stop(); // issue I2C stop signal
}

unsigned char BCD2UpperCh(unsigned char bcd)
{
  return ((bcd >> 4) + '0');
}

unsigned char BCD2LowerCh(unsigned char bcd)
{
  return ((bcd & 0x0F) + '0');
}

int Binary2BCD(int a)
{
   int t1, t2;
   t1 = a%10;
   t1 = t1 & 0x0F;
   a = a/10;
   t2 = a%10;
   t2 = 0x0F & t2;
   t2 = t2 << 4;
   t2 = 0xF0 & t2;
   t1 = t1 | t2;
   return t1;
}

int BCD2Binary(int a)
{
   int r,t;
   t = a & 0x0F;
   r = t;
   a = 0xF0 & a;
   t = a >> 4;
   t = 0x0F & t;
   r = t*10 + r;
   return r;
}

int second;
int minute;
int hour;
int hr;
int day;
int dday;
int month;
int year;
int ap;

unsigned short set_count = 0;
short set;

char time[] = "00:00:00 PM";
char date[] = "00-00-00";

void main()
{
   I2C1_Init(100000); //DS1307 I2C is running at 100KHz

   CMCON = 0x07;   // To turn off comparators
   ADCON1 = 0x06;  // To turn off analog to digital converters

   TRISA = 0x07;
   PORTA = 0x00;

   Lcd_Init();                        // Initialize LCD
   Lcd_Cmd(_LCD_CLEAR);               // Clear display
   Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off
   Lcd_out(3,1,"Time:");
   Lcd_out(4,1,"Date:");

   do
   {
      second = read_ds1307(0);
      minute = read_ds1307(1);
      hour = read_ds1307(2);
       hr = hour & 0b00111111;
       ap = hour & 0b00100000;
      dday = read_ds1307(3);
      day = read_ds1307(4);
      month = read_ds1307(5);
      year = read_ds1307(6);

      time[0] = BCD2UpperCh(hr);
      time[1] = BCD2LowerCh(hr);
      time[3] = BCD2UpperCh(minute);
      time[4] = BCD2LowerCh(minute);
      time[6] = BCD2UpperCh(second);
      time[7] = BCD2LowerCh(second);

      date[0] = BCD2UpperCh(day);
      date[1] = BCD2LowerCh(day);
      date[3] = BCD2UpperCh(month);
      date[4] = BCD2LowerCh(month);
      date[6] = BCD2UpperCh(year);
      date[7] = BCD2LowerCh(year);

      if(ap)
      {
         time[9] = 'P';
         time[10] = 'M';
      }
      else
      {
         time[9] = 'A';
         time[10] = 'M';
      }

      Lcd_out(3, 6, time);
      Lcd_out(4, 6, date);
      Delay_ms(100);

   }while(1);
}


texts:
The following description is taken from maximintegrated website (this link specifically), and after reading and trying to analyze the control technique it still does not make sense to me:
1 - In the figure it shows a boost converter, and it reads:

This duty cycle change then moves the output voltage to reduce the error signal to zero, thus completing the control loop.

From my point of view if that \$V_{ERROR}\$ is supposed to converge to zero for a steady state output voltage, the duty cycle should be kept steady at 0% since \$V_{RAMP}\$ will always be greater than \$V_{ERROR}\$ and the latter seemingly not subject to variations, which cannot be true since it meant the circuit would stop switching. A comparison I have used to understand it better is when I think of a PI controller, which brings the error to zero but has a memory in its output value, so it only responds to small variations once the steady state value is reached.

My question is: How is this control loop supposed to keep the output voltage steady regardless of for instance, load variations, if the error being reduced to zero would actually stop the switching?
By the way in the timing diagram they've inverted \$V_{SWITCH}\$ since it should be high when \$V_{ERROR} > V_{RAMP}\$, but it does not matter to the main question since it must've been a little mistake.
EDIT:
Following the main discussion, the figure below shows the circuit I have been inspired from to get this control loop done. It comes from this video in which the designer himself references maximintegrated's website.

I tried to replicate the idea using an op-amp, a behavioral voltage supply and a pulse source to generate the triangular wave in LTspice, trying to replicate the idea described in maxim's document and here are the results.

I have set a value of \$V = 5\,V\$ which is the reference for \$ 50\,V \$ in the output since \$V_{feed} = 0.1\,V_{out}\$.
Result: As you can see, my voltage level in the output is \$V_{out} \approx 25\,V\$, which is not what I have set the system for. Also, I tried changing values of the load and the output voltage also changes and that's not what I wanted either.
Finally, I'm probably mistaken in how this controller works and would really like to find out what is wrong.
Thank you in advance


texts:
I am referring 7" LCD (P/N : S070WV20-CT16) for interface with host controller LPC1769.

Datasheet
Part of datasheet I've added here:

TFT has data pins ( R0-R7,G0-G7,B0-B7), Control pins
(Mode,DE,DCLK,VS,HS,RESET,DITH), power pins (VCOM,DVDD,VGH,VGL,AVDD)

For power requirement we can use dedicated boost converter to meet up all power requirements (VCOM,DVDD,VGH,VGL,AVDD). For eg.Link

So, my question is,

For data Pins ( R0-R7,G0-G7,B0-B7) and Control pins
(Mode,DE,DCLK,VS,HS,RESET,DITH).. can we assign LPC1769 GPIO pins directly to these pins of TFT?

please someone explain.Thanks.


texts: Photodiode Trans impedance amplifier design

texts: Am designing a trans impedance amplifier for photodiode from first sensor PS-100E.Am using LM 358 op-amp.To calculate the feedback resistance ,I should know the short circuit current of the photodiode.However I could'nt find it in the datasheet.I need help to calculate the short circuit current.Thank you


texts: What does "looking into the emitter" means in small signal analysis?

texts:
In small signal analysis I had to go through the words "looking in to the emitter".

According to this looking the resistance we take differ \$r_e\$ and \$r_{\phi}\$. Can you explain what this looking into the emitter means? It's bit confusing.


texts: If I'm not wrong, is the term "Power cube transformers" is less commonly used to refer "A.C/D.C Adapter"? I couldn't find the use to this term.


texts:
I'm building a Tesla coil and part of my schematic is a 4.7uF PP MKP Capacitor and at the moment i don't have one. Luckily enough, I have other capacitors of equal value but not material. So I was curious as to whether another material would work instead of metalized polypropylene film. Look right before the primary coil on the right side of the image.

And please excuse any mistypes with the letter "I" I'm missng that key on my board.

Here s the schematic. Enjoy!!


texts: Given the dynamic and static power consumption how does one determine the total power for the capacitive load?

texts:
I get that the capacitive load is determined which is also indicated by this question:
 $$\frac{Power}{Voltage^2 \times frequency} = Capacitive Load$$

However, I am not sure how power (which is given in Watts) is determined when given both the dynamic and static power consumption and unfortunately my textbook doesn't really give any suggestions either. My guess is power would be equal to either dynamic - static or dynamic + static, but I don't which one would be correct, if either are correct, and more importantly why that statement is correct.


texts:
Could you please explain how a 'Low-Drop Voltage Tracker' IC works. For example take  the     TLE4250G from Infineon. what is the difference between LDO and Low-Drop Voltage Tracker .
Regards
Hari.


texts: Inductive Proximity Sensor Proteus Simulation

texts:
Do you know how can I simulate in Proteus a similar component to the Inductive Proximity Sensor? I don't find it on the default libraries

Is it recommended to simulate every single component?


texts: What is the typical voltage of power distribution in rural North America?

texts:
I mean the electrical utility power that connects to the transformer outside of the home or other buildings.  i.e. what is the primary winding voltage of the transformer having 220 VAC center-tap secondary?

i have heard as high as 13 kV, but that seems kinda high.  isn't it more like 4 kV?


texts: Making a bigger transfomer core by stacking multiple smaller cores

texts:
Does using a number of stacked EI or EE cores in the place of a bigger one (respecting the know magnetic characteristics) would pose any substantial difference?1

There's even manufactures that sell glued cores, but I think 4 stacked cores is the maximum I have seen (ferrite cores not laminated ones).

UPDATE:

The idea is not to "miniaturize" the core, in fact they may be heavier and bigger than a single core, but to have access to high power cores if your local market is not selling larger cores.

In fact, the above manufacturer shows that even it sells some bigger cores as glued/united small cores and the specified magnetic characteristics from then

Single core:

Same core stacked:

Both images from Thornton products catalog.


texts: 11 Column 84 Row LED Matrix MicroController?

texts:
I am a total novice and have the need to make a 11x84 LED Matrix for a project I am working on, and was wondering if this would be possible. I made an 8x8 prototype but have realized that my ARDUINO UNO will not have enough pins for this task.
Are there any micro controllers with enough pins, or any other ways around this?

Any advice appreciated.

Thanks


texts:
What is the relationship between crystal oscillator frequency Vs Die size?

Why it is smaller Die size over the high frequency ranges and bigger Die size in lower frequency ranges?


texts:
I want to use pololu step-up converter https://www.pololu.com/product/2836
 in order to power a 5V device with two Ni-Mh batteries (1.3V each). It has only Vin, Vout and GND connectors. I've checked with voltmeter the batteries together and they give stable 2.6V, which should be, according to specs of the converter, enough to make it work.

I've tried wiring as below

but the voltmeter shows 0.48V, when I'm expecting 5V...

I don't know what am I doing wrong... Is this wiring wrong or my converter broken?


texts: Eeschema, least painful way of changing pin order per symbol instance

texts:
I'm considering using Eeschema to create block diagrams. More or less just lots of abstract rectangles with ins and outs, interconnected. It will look like xcos/Simulink.
For better readability, I'd like to be able to disentangle the wiring by adjusting symbol's order of pins ad hoc. Strictly speaking, symbol instance's order of pins.
Example: swapping spontaneously VDD and GP3 of U6 on the snippet below, and maybe pushing GP5 up and GP4 down, but only of U6 and not all PIC_8_PINS; connected wires should remain connected (I'll have to move them around for a better appearance, of course).
Question: Cloning a symbol for every variant of appearance sounds like a hassle. Does anybody know a better way?
I'm currently using MS Visio where I can freely move pins around, but I want "something electrical" with nets and buses and smart highlighting instead of, well, just lines. This is a specific question about eeschema, though, thus here and not on softwarerecs.


texts: Signal Conditioning of the conductive Polymer?

texts: I have a conductive piezoresistive polymer which gives the resistance changes according to the applied force and strain. What could the first step to start the signal conditioning. The goal of the Signal conditioning is to have the signal output is between 0-5 volts for the input force.


texts: Are virtual-functions called at a high frequency suitable for embedded systems?

texts:
I have a (reasonably powerful) 32-bit MCU.
Would it be unwise to design my system using OOP principles - mainly virtual methods?

I have a virtual method which would be called around 1000/second.
Could this be a problem?


texts: Rotation speed detection circuit (Wind turbine)

texts:
I need to determine the rotation speed a wind turbine generator. To do this i'd like to measure the frequency of the three-phase signal provided by the PMG generator

The three-phase signal tension range is 0V - 300V and the frequency range is 0-70Hz.

i use stm32 microcontroller to compute the frequency so i need a 0-3.3V square shape signal input.

I designed a circuit to turn the AC signal into a squared shape 3.3V signal:

I send one phase of the generator to a rectifier 1n4007 diode to remove the negative tension. Then a 3.3V zener clip the signal. The opto-isolator protect the stm32 from high tension and create a beautiful 3.3 square shape signal

question: is it safe, is it reliable ?

Thank you !


texts:
I have an ATTiny85 with a PWM output (freq. aprox. 1kHz). Connected to this pwm output pin is a NPN general purpose BJT (2N2222) with base resistor of 1k. A LED is in series with this transistor (before the collector). The LED has a current limiting resistor of 470R.

Everything seems to work pretty good, but if my PWM duty cycle is very low (< 30%), then something strange happens. Every few seconds the LED flashes/flickers. But it's not the well known PWM flickering. My flickering is very irregular (just every few seconds).

I used a oscilloscope and did some probing. The PWM output signal directly at the microcontroller pin was ok in my opinion. Then I checked the conductivity of the transistor, connecting my scope probes to the vcc and emitter of the transtistor. This gave me the following result (see picture).

Am I correct, the the transistor is not properly switching off, and "skips one cycle"? This could be the reason, why the LED flickers?

Now the most important questions: Am I using the wrong transistor type - or should I switch to a mosfet-based solution? What would you suggest, to solve this issue?

Thank you very much. You help is greatly appreciated!

Here is the schematic:


texts: Is It Safe To Test A Pc With A Possiblly Burnt PSU

texts:
about a year ago my dell desktop pc wasn't turning on. the power button kept blinking orange. so I thought maybe something was loose or switched off. I looked at the back of the psu and saw a red switch. thinking it was the on/off switch, I slided it to the other side and instantly the computer went 'BANG' with a zapping noise. I instantly turned every thing off and the pc has been in a storeroom since. I later found that I had changed the psu voltage switch from 240 volts to 115 volts

now my question is that would it be safe to plug in this pc to the mains just for testing. I know 99% it will probably not work but do you think its safe interms of electrocution or further damage or bangs.


texts: Zener Diode vs Voltage Divider vs DCDC Converter vs Voltage regulator IC

texts:
As the title suggests I am looking for a way to drop 12V to 5V**. Which circuit should I use? And if I am going to use one, Why can't I use the others in the list ? I am looking for:
1. If the current going in is the same as the current going out.
2. Least heat dissipation.
My options :
Voltage Divider ; DCDC Converter ; Zener Diode ; Voltage Regulator IC.

** I am trying to run 4-5 servos (5V) using a microcontroller (PIC 18F452) and also 4 DC motors(12V).


texts: Choosing the right resistor for a LED circuit

texts:
I am planning to do a high power LED lamp, and I would need some checkup for my calculations.

I plan to use some CREE LEDs from AliExpress, which claim to have an input voltage of 3.4-3.6V and a power of 3W. The idea is to run 12 of them in parallel from an ATX power supply, connected to the 3.3V rail. The leds will be connected with thermal tape to a big strip of solid aluminum for cooling.

I would try to be on the safe side and run the LEDs at only 2W each, meaning that each LED will eat up about 600 mA. So, I need to supply 0.6 * 12 = 7.2A. The good news is that my power supply can provide up to 15A on the 3.3V rail, so that should be fine.

Now, from my experience with small LEDs, usually is a good idea to insert a resistor. For the overall circuit, I would need a resistor of 3.3/7.2 = 0.5 ohm. And the resistor would need to withstand about 23.7W. Which seems big to me.

The question is: do I really need this resistor, since 0.5 ohm seems low enough for me (I'm also considering the about 1m wiring that I expect to have some resistance at this current)? Do such resistors commonly exist?


texts: Is no-load to stall amp draw linear with DC motors?

texts:
I have two DC motors with no-load current draw of 200mA. The datasheet goes on include a stall-current draw of 2.2A.

The torque is given for both extremes. Considering you know the torque that is being exerted (and presumably that is the force required to be exerted to stop the motor from turning) is this relationship linear?

I am concerned because I will obviously load the motors when using them but am not sure how to calculate the estimated current draw under arbitrary load. Do you simply throw the contraption together and measure the current being drawn by the motors and when you see that value approaching the stall current then its obvious you are overloading your motor?

Actually, it is linear. I found this online just now. But I am still concerned with the second part of my question regarding calculating loaded current draw. From the graph below its obvious you can determine current by a given torque load - but how do you calculate that? Or what other methods are known?


texts:
I finished the schematic for my 2.4GHz microstrip Wilkinson power divider. I am moving to the layout and trying to do the EM simulation, but I cannot figure out how to put a lumped element in the layout design. This is the error I am getting:

If anyone could help me put lumped elements into the EM simulation that would be greatly appreciated!! Thanks in advance!


texts: Synchronous rectification name explanation

texts:
In different power supply topologies synchronous rectification is used to improve efficiency.
The diode is then replaced with a MOSFET, which emulates the behaviour of the diode  .

My question might be straightforward but has been bugging me for quite some time.
Here it comes:

Question: Why is it called synchronous rectification? what is synchronous?


texts:
I'm new here and I trying to figure out how to work with an ADC. I've read a lot of stuff and I believe that an AD converter it's "very simple" to use. What I mean: Plug the analog source to one side and get the digital source on the other side. However, this is theory - it's not that simple in real life.

What I'm trying to do is, use the PCM1807 (http://www.ti.com/lit/ds/symlink/pcm1807.pdf) to get signals from a cardioid microphone.

I was trying to figure out how to make the connections of page 25, but what I didn't understand is do I need that MCU, that AND port with MASK and PLL, and that DSP or AUDIO PROCESSOR to make it work?

Sorry for the newbie question!

Thanks.


texts: How to calculate Multistage Filter Design overall cutoff frequency when each stage has different cutoff frequency

texts: How to calculate Multistage Filter Designs overall cutoff frequency when each stage has own different cutoff frequency


texts: Beginner trying to understand flip flops

texts:
I'm trying to understand how JK and D flip flops work. I am generally very airy when it comes to these topics and was hoping someone could explain in layman's terms how these two circuits work.

It is my understanding that a JK flip flop takes two inputs, j and k, returns two outputs, q and not q, and a(n) (inverted?) clock signal. I read here, http://forum.allaboutcircuits.com/threads/jk-and-d-flip-flops-which-one-to-choose.32024/, that it has four functions: SET, CLEAR, HOLD, or TOGGLE.

Likewise, D flip flops take one input, d, returns two outputs, q and not q, and inputs a clock signal. They only have the two functions SET and CLEAR.

What does it mean when a flip flop performs a function like SET, CLEAR, HOLD, or TOGGLE? Does this alter output? Current state? How? Why?

When attempting to follow a circuit that implements both, I start with a clock signal that goes into each flip flop. From there, I really have no clue how to trace what's going on.

As an example, the clock signal first enters JK flipflop, then D flipflop. The Q for the JK flipflop returns an output, and the not Q is then input as D in the D flipflop. The Q for D flipflop then becomes an output, and the not Q gets input into the J and the K (I'm assuming with a new clock signal, which essentially restarts the whole process) of the JK flipflop.

I would like trace the output and current state for each time the process repeats. Ultimately, I am trying to determine the "transitions" between each state. I see multiple examples on other websites, but all use different variables representing different things and it throws me off huge.

Any help explaining these complicated buggers is appreciated!


texts: How do I determine the distance from a magnet using Magnetometer?

texts:
I have a triple-axis magnetometer and a magnet, and I am trying to calculate the relative position of the magnet from the magnetometer.

The magnetometer outputs the strength of any fields detected in each of the (X,Y,Z) directions, and I understand that I'll have to compensate for the Earth's own field, as well as how to determine the relative location of the magnet, but what I do not understand is how to determine the distance that the magnet is from the magnetometer.

So my question is: assuming that I have a magnetometer pointed exactly straight towards a magnet, and the magnetometer is outputting the field strength, is there an equation that I can use to determine the distance that they are apart?

I have attempted doing some research into this, but all the results I am finding vary from one another incredibly. Any help/advice would be much appreciated.

Edit 1: I feel like I should note that I'm using a cylindrical magnet. Would the calculations be different if I were to use a rectangular one?


texts:
From the paper https://ir.nctu.edu.tw/bitstream/11536/5095/1/A1979JE36000027.pdf
I'm trying to understand this MOSFET circuit which creates negative resistance. Whilst the paper explores how it works, I'm not really understanding it.
I've tried simulating it in SPICE however I'm not really seeing the negative resistance effect, i.e negative current is proportional to voltage. A general overview of this circuit would be greatly appreciated as well as some indication of how to recreate it in LTSpice would be handy.
Equally any more examples of MOSFET based negative resistance would be helpful to understand it deeper.


texts: Experimental low-pass filter construction using a NanoVNA?

texts:
Suppose I wanted to construct a no-solder plug-board or rats-nest low-pass filter for VHF frequencies, but without the "proper" circuit substrates, design software, or test equipment.
Could an inexpensive NanoVNA be used to test and incrementally improve a VHF filter construction using random junk box caps and hand-dimensioned hand-wound scrap-wire coils, via trial-and-error ?
If so, how?


texts: Arduino, GSM quadband module and gas sensor connection anyone?

texts:
I have an Arduino, a GSM quadband module and a gas sensor.

I could only find connections of GSM to Arduino and gas sensor to Arduino. Anyone who can give me a connection diagram of three devices?


texts: Charging a battery with kinetic energy (rotating wheel)

texts: What would be a simple setup that would allow me to spin something kind of like a servo motor but would result in power that can be used to charge a battery when you spin it yourself.


texts: Amplifier transistors not receiving change in base voltage... do I look forwards or backwards?

texts:
So I'm working on diagnosing a CRT scope that isn't responding to the horizontal controls; the trace is off screen. The two X plates are each being driven by 2 transistors in line. One X plate has over 100V going to it, and its transistors' base voltages are changing in sync with the horizontal position pot as I turn it. However, the other X plate which has 0V on it, its transistors' emitters and collectors have a sporadic 2-3V jumping up and down, and its bases aren't responding to the horizontal position pot.

My gut tells me I need to look upstream of the transistor's base (the one not responding to the horizontal position pot.) Is this correct?

Or could the problem exist in the emitter/collector circuit somewhere, and be interfering with the base of the transistor?

I've got a diagram if you need one.

Thanks a heap!


texts: Please help me with finding if I need to add a resistor to my circuit

texts:
I want to connect 3 4V LED strips in series to a 12V, 1A supply. Each strip requires 250mA current to operate. This makes a total of 750mA required current for all 3 strips. My concern is how should I deal with the remaining 250mA?
Should I add a resistor? How much ohm resistor should I add?
It will be so nice of the responder if he/she shows me how to do the math to such.


texts: How do I work out the time when given current in a RC circuit?

texts:
So this exam question looked straight forward, but I can't get the right answer.

I'm trying to find the time, from when the switch is close,that the current will equal 2mA.
I've used a few formulas but none give the right answer.

What am I doing wrong?

Also the tau and time confuse me a bit.

Any help would be greatly appreciated.

My calculations


texts: Multi-layer board drill pair recommendations to reduce PCB cost

texts:
I'm designing a simple 6 layer board with following as core components.

http://www.ti.com/lit/ds/symlink/tm4c123gh6pm.pdf
http://www.ti.com/lit/ds/symlink/afe4403.pdf

I using this stackup

Now I'm looking at the drill pairs so that will give optimal performance by not bumping the cost. I heard that buried via will incur more costs compared to blind or thru hole via.

Please recommend some multilayered board drill pair for simple typical 6 layer board.

Thanks


texts: Why my boost converter is not boosting the voltage?

texts:
I am trying to build a boost converter using LT3517 with 5V input. LED and input voltage(5V) is constant for our application. I need to tune the circuit between this and the current across the LED should be 500mA as per our application. so I put 1.65 ohms current sense resistor.

But 5V input is not switching/boosting the voltage. can i know the reason for it?

what is the mistake i made in the below circuit?
How can I boost my voltage?


texts: Analysis of a circuit with transformer, R and C components

texts:
I am not able to solve the above problem. I don't think my equations are wrong but I am not able to solve them. Please help me with this.
The answer given in my workbook is 3.93cost(3t+59.9)
Method A

Method B

This is not a homework problem. I was practicising problems when I came across this one.


texts:
I have a BeagleBone Black:

$ cat /etc/dogtag
BeagleBoard.org Debian Image 2015-03-01
$ uname -a
Linux beaglebone 3.8.13-bone70 #1 SMP Fri Jan 23 02:15:42 UTC 2015 armv7l GNU/Linux

There's an updated image available BeagleBoard.org Latest Firmware Images. The updated image is for Debian 8.2, and its dated 2015-11-12 (sha256sum 4714268365500e4c...).

According to eLinux's BeagleBoneBlack | Debian, I simply need to uncomment the following line. I verified I have init-eMMC-flasher-v3.sh in that location.

##enable BBB: eMMC Flasher:
#cmdline=init=/opt/scripts/tools/eMMC/init-eMMC-flasher-v3.sh

I'm running into trouble because I'm not sure what else is needed. I don't see a treatment in the wiki, the Debian docs are a mess (and don't really apply), and the script lacks head notes, comments and usage.

# cat /opt/scripts/tools/eMMC/init-eMMC-flasher-v3.sh | grep "\.xz"
#
# cat /opt/scripts/tools/eMMC/init-eMMC-flasher-v3.sh | grep "\.img"
    cp -v /boot/uboot/u-boot.img /tmp/boot/u-boot.img || write_failure
    rsync -aAx ${rsync_progress} /boot/uboot/ /tmp/boot/ --exclude={MLO,u-boot.img,uEnv.txt} || write_failure

And:

# /opt/scripts/tools/eMMC/init-eMMC-flasher-v3.sh --help
Starting eMMC Flasher
-----------------------------
Checking for Valid BBB EEPROM header
Valid BBB EEPROM header found
-----------------------------
copying: [] -> []
lsblk:
NAME         MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
mmcblk1boot0 179:16   0     1M  1 disk
mmcblk1boot1 179:24   0     1M  1 disk
mmcblk1      179:8    0   3.7G  0 disk
├─mmcblk1p1  179:9    0    96M  0 part /media/BEAGLEBONE
└─mmcblk1p2  179:10   0   3.6G  0 part /
-----------------------------
df -h | grep rootfs:
rootfs                                                  3.5G  1.9G  1.4G  58% /
-----------------------------
Error: [] does not exist
writing to [] failed...

Image name

Do I unpack the *.xz archive so that its filename is bone-debian-8.2-tester-2gb-armhf-2015-11-12-2gb.img (that's the filename in the *.xz archive)? Or does it need to be named something else? Or should I do nothing and just reboot?

fstab

Also, do I need to add an fstab or mtab entry for mmc0 before rebooting? Or should I do nothing and just reboot?

Here's what I see when I install and remove the microSD card:

# dmesg
...

[ 9493.952565] mmc0: new high speed SD card at address e624
[ 9493.956686] mmcblk0: mmc0:e624 SU02G 1.84 GiB
[ 9493.973345]  mmcblk0: p1
[ 9504.049054] mmc0: card e624 removed
[ 9504.243331] mmc0: host does not support reading read-only switch. assuming write-enable.
[ 9504.246933] mmc0: new high speed SD card at address e624
[ 9504.249514] mmcblk0: mmc0:e624 SU02G 1.84 GiB


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I am planning to use this USB connector but I am having trouble finding the pin-out:

https://www.digikey.in/product-detail/en/USB-A1SSW6/ED2991-ND/2677752

I checked 3-4 different manufacturers and all of them give just the drawing and package info. Any help would be very much appreciated. Thanks


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I know potential is always about difference so you can't just measure a potential but it's difference with some other potential.

Let's say I have a GND and two inputs each one 0-5v and I have a ADC measuring 0-1V being 0.0 v == GND. I can't change the reference.

I want to amplify small differences between the inputs and measure the difference with the maximum resolution. Is there an easy way to subtract V1 - V2 and supply the result to the ADC?


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What is the component that is represented with two horizontal lines like a capacitor with three Ground Chassis lines connecting them and a + at the top and a 10μ label.

See picture below (top right corner):


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Let's say I'm doing a two-tone test to measure intermodulation distortion in an RF power amplifier. I look at my spectrum analyzer1, and I see this:

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1I don't actually have a spectrum analyzer, which is why the Y axis is in dB and not dBm. This screenshot is GNURadio doing an FFT on the audio output of a 2nd receiver which I'm using as a poor man's spectrum analyzer.


texts: Power calculation and Ohm's Law for Reactance

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Hi I have the following question:

V = 120V,
I = 10 A, I lags V by 60degrees

simulate this circuit – Schematic created using CircuitLab

The load consists of a resistor and an inductor in series.
What is the reactance of the inductor?

The way I have tried to solve it:

Since the current lags the voltage 60 degrees:
\$ I = 10 \angle 60 \$

\$V = 120\angle0 V\$

\$V = IZ\$

\$Z = \frac{V}{I}\$ (1)

\$= \frac{120\angle0}{10 \angle 60}\$

\$ = 6-10.4j\$

Hence the reactance \$X_L = -10.4 \$

I know this is wrong, because by convention inductors have positive reactance!
So where am i going wrong?

I could use power formulas for S, P and Q to solve this, but i would like to know why doesn't the above work?
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Cheers!


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Above on the left, if the circuit is in linear mode and if a sinusoidal small vbe applied to its base, there will be an ic collector current which is composed of a DC offset Ic0 plus an AC component call it ic. The total collector current will look like this:

Considering the above total collector current ic, what can we say about the current direction? Does AC part of the current flow into the Vcc back and forth or not(in reality)? Because in AC analysis we short the Vcc ground as if the current flows into Vcc back and forth. I hope I could articulate where I'm confused.