texts: Soft-Start Circuit with Premature Loading

texts:
BACKGROUND

I am designing a board to convert high voltage (~400V) DC down to medium voltage (~30V) DC to provide power to subsequent boards. In its simplest form, my board will consist of the DC/DC converter and a large capacitor bank for large transients.

The DC/DC converter I am using has a limitation on it, where it can only supply 10% of its maximum rated current until it has reached 50% of its nominal output voltage. The capacitor bank consists of ~20mF of capacitance. This caused the need for my soft-start circuit.

My soft start circuit is made of an high power N-channel MOSFET (FDMS86540) and a high side gate driver (LTC7003). It is designed to limit the inrush current to below 750mA until the capacitors are fully charged and then cause minimal power dissipation (R_on of MOSFET). Below is a schematic for it.

The LIMITER_IN pin ties to the output of the DC/DC converter, while the LIMITER_OUT pin feeds into the capacitor bank, as well as the subsequent boards.

THE PROBLEM

The issue I am running into is that the subsequent boards have components, such as linear regulators, that will turn on(enable/run pins tied to output voltage through resistive divider) before the capacitors are fully charged. Because of this, they are drawing loads of larger than 750mA, causing the capacitors to discharge and the soft start circuit is never bypassed. The idea is that once, the capacitors are fully charged, the current is no longer limited and the DC/DC converter will supply the current to the loads, and the capacitors are solely there for transients.

I could potentially put a switch at between the capacitor bank and the subsequent loads, but for my current application that would dissipate an unnecessary amount of power. Is there a way for me to adjust my soft-start circuit to account for the premature loading on the cap bank? If not, are there other architectures I can look at to limit the inrush current of the cap bank? The primary goal is to minimize dissipated power after the soft-start completes.


texts: Is a fuse necessary after a power supply?

texts:
I am working on a project with some 12V LED strips and am planning on powering them with a Mean Well LRS-150-12 power supply (12.5A @ 12V).

My total LED strip load is about 10A.

I was planning on wiring a fuse holder to the output of this power supply with a 10A fuse for protection, but I was just thinking, is a fuse actually necessary in this case?

The power supply can output 12.5A which is just slightly more than the LED strips can draw. The wiring can handle 12.5A just fine.

Is there a failure mode of a power supply that could cause more than 12.5A to be outputted, which would necessitate a fuse, or can I rely on the power supply limiting the current to 12.5A @ 12V which everything can handle so no fuse is necessary?


texts: Nodal analysis for current controlled current source

texts:
Okay here I go. I just started learning nodal analysis technique but I feel its difficult in solving the circuits consisting of dependent current and voltage sources.

Im unable to solve this circuit.

The current source is a dependent current source and whose value is 180 times Ix and Ix is the current flowing through the 0.7 v battery.

Generally to solve this type of circuits we find a relation to express Ix in terms of node voltages / resistance. example Ix = (V2 - V1 ) / 500 ohms .  But here there is no resistance in the 0.7 v branch voltage. I am unable to find a solution to solve it.
Could anyone kindly explain me the solution to this circuit.

NOTE I have found a solution by finding the thevinin's resistance across 0.7 v battery and replaced it with Rth in series with 0.7v and I have got the solution but I want to know, Can we get it using only KCL equations (nodal analysis) ?

Please help me in solving this circuit and kindly explain it with the KCL equations. Your help is greatly appreciated. Thank you


texts: High pass filter for use in amplifier circuit

texts:
I've designed an amplifier for a small ac signal (amplitude of around 5mV, frequency 252kHz) with a BJT (2N2222.)

The BJT is set up in a common emitter amplifier configuration, with the biasing resistors set up to provide a constant 0.7Vdc to the base.

I used blocking capacitors C2 and C4 to remove the dc bias by acting as a high pass filter.

However, even though I designed the circuit to have a voltage gain of 100, with cut off frequency of around 200kHz, I found my ac input signal was still being attenuated.

By changing the cut off frequency to 20Hz, I achieved a gain of close to 100. However, even by changing the cut off freq to 100kHz, my output signal is still attenuated.

Why is this?


texts: Can I use solid state output and relay output with the same components?

texts:
So I have a OTB1E0DM9LP Schinder Electric I/O distributed module and I want use it'output to control some 24v electro-valve's and some 24V contactors.

The module have

2 Solid-state outputs of 24V 0.3A
6 Relay outputs 30V 2A

I'm having 3 valves and 5 contactors.

Can I use the relay and the solid state output to control both the valves and the contactors?

This means I can switch max 8A with the relay and 360mA with the Solid state?


texts: Regarding slew rates, what would be the minimum for amplifying audio using an op-amp?

texts:
Many, many choices. And this is just Microchip's offerings.

I'm going to be amplifying by a maximum of 5x using an op-amp. So I choose an op-amp with a GBWP of 50 kHz * 5 = 250 kHz. That still leaves many op-amps. What slew rate should I be looking for? (with low distortion on the output.) And are there any other parameters to look out for, like input noise and offset?

EDIT: It seems I need to clarify. I'm only looking for a single channel op-amp for amplifying a mono signal with reasonable levels of distortion. I'm not looking for high quality prosumer gear audio.


texts:
I'm working on PIC18F8722 to generate PWM for 50% duty cycle. I have obtained the PWM and now I need to count the PWM pulse. As per my knowledge we can use timers to generate and count those pulses with a counter. I 'm not understanding how exactly to do it. Any advice is appreciable.

Thanks!


texts:
I bought a very old Philips oscilloscope some time ago (see my post. This is a Philips PM 3253). Although this Philips really has a lot of features, I cannot really use it well, since I cannot do good readings below 1 MHz because of the bad screen (focus problems, lines stay very long on the screen, or the signals are 'clipped').

Now I saw another one at a local 2nd hand site: Metrix OX8050

I was wondering if the probes between these two scopes (or actually in general in case this one is already sold) are interchangeable.


texts:
Can i only  use the MOV command (for bit addressable registers like PSW,ACC as well as ports ) with the carry bit?

Is the command :
MOV PSW.4,ACC.4 work with the assembler?
if not why?
How can i directly move a bit from one bit addressable loacation to the other and between SFRs?

;-----------------------------------
I am using EDSim51dI version 2.1.14
;----------------------------------

ALSO,
i am having problems using commands for bit addressing of PSW in the sim...!

EX: These instructions dont seem to work

org 0000h
mov psw,#0fh
mov c,psw.4

please help?
Urgent..!


texts:
This question is similar to Zener Diode Selection for Relay but the focus is in how to select the voltage for optimum or near optimum release time.

With the circuit below, how does one select the zener voltage ?

simulate this circuit – Schematic created using CircuitLab

I've removed the values from the circuit because I'd like to know how to select a zener for any relay with any coil voltage.

Added
After thinking about it for a bit, is the follow reasoning sound ?

$$ P_{zener} \geq V_z * I_{coil} $$
$$ V_z \leq \frac {P_{zener} } {I_{coil}} $$'


texts: Dual power supply from a single AC adaptor

texts:
I designed a microphone preamplifier based on a single op-amp. It works perfectly using two 6-volt batteries.  However, I need to power it directly from AC.

I found a 9 V AC rated wall-wart, but it is not center tapped so I need to find another way of making dual-voltage supply. How do I do that?


texts: Stopping overvoltage with Solar on Lithium ion tool batteries for an audio application

texts:
I am using two Lithium ion tool batteries (18V) to get a 36 V line. When fully charged it is greater then 40V. As they are tool batteries, undervoltage protection is already built in.

I want to be able to charge these batteries with a very high voltage solar panel (>50V). I am not interested in efficiency. I am only worried about overvoltage protection for the batteries.

Is there a cheap way to have charge protection with this system. The application is audio, so violent audio band waveforms (< 24 kHz) is not acceptable on the power lines.


texts: Adding logic to existing 240 V AC circuit

texts:
I have some heating circuitry which runs on 240 V. I need an output from an XOR gate from two points on this circuitry. I was thinking I could do the gate with relays but couldn’t find any relays with a 240v coil that weren’t large and expensive.

The diagram below shows a part of the heating circuitry around a zone valve and two points that can either be 240 VAC or 0 V. I want to read these points through an XOR gate.
Is it best for me to just buy these 240 V relays and use them or is there a neat way to bring down the 240 V input to a sensible logic voltage and use cheap low voltage coil relays? I’m open to alternatives to relays as a whole and don’t mind what voltage the XOR output is.


texts:
Input rating or max current?

I want to install two 5 kW inverter air cons and reading the specifications I'm a bit confused. The rated power input is 1.22 kW each so together they draw approx 2.5 kW so I was thinking to run a 2.5 sq mm power line and use a 16 A RCD to supply BOTH outdoor units.

Then I read on the outdoor unit tag that the input is 1.22A but max current is 13.5 A? Does it mean that at full load they can draw up to max current for some period?

I will run them together to cool 2 large interconnected areas at the same time, never independently.  If so I will need two separate lines with a 16 A RCD each or should I go from the input data for my calculations and stick with one line for both?


texts: Upgrade a cordless screwdriver (16.8 V) to Li-Poly

texts:
I'd like to upgrade my cordless screwdriver/drill to use lithium polymer batteries. Problem is, the screwdriver uses 16.8 V at the moment (14 NiMh 1.2 V cells).

So, using lithium polymer batteries with 3.7 V each, I have the choice between 4 cells (14.8 V) or 5 cells (18.5 V).

14.8 V would be an expensive downgrade - especially for the drilling. I am not even sure if this would work (but probably it would, right... I am not experienced with these things).

18.5 V on the other hand would be a difference of 1.6 V or a bit more than 10 %. Would the motor survive that?

Suggestions on how to do this upgrade are most appreciated!


texts: Why would a CPU+Wi-Fi module supplier not mention both memory and memory bus?

texts:
Today I found Imp - a CPU together with a Wi-Fi module with an antenna included and all packed into the size of an SD card. The specification says nothing about memory and doesn't mention a memory bus.

I always thought that the amount of memory is kind of very important for an embedded system. Okay, maybe there's no memory built in, but then the user would have to add his own memory and that would require a memory bus and the memory bus specification would also be important because it would affect what memory can be used and how fast it would work. Yet neither is mentioned.

Why would the supplier not mention both memory and memory bus in such a module description?


texts:
I am using a stepper motor for a project, it is the first time I've used one. The internet said it was very simple and easy but that's not true for me.

I bought this motor from digikey

https://www.digikey.ca/product-detail/en/digilent-inc/290-028/1286-1219-ND/7068780

and used this tutorial to wire it up. Except mine is a 5V stepper motor.

https://itp.nyu.edu/physcomp/labs/motors-and-transistors/lab-controlling-a-stepper-motor-with-an-h-bridge/

I used the Arduino stepper motor one revolution example. Set the stepsPerRevolution to 64 as per data sheet.

The motor turns less than a quarter turn, no torque and only draws 8mA. I can not get it to a full revolution or have any torque.


texts: 'V' groove routing at cheap PCB manufacturers

texts:
I am designing some PCBs, which I intend to prototype, and then get small volumes produced for personal use at a cheap PCB house such as Itead, DirtyPCBs, or Seeedstudio Fusion PCB. These board houses all charge about $12 for 10 copies of a PCB up to 5x5cm. My design will stick into a USB port like a little dongle, and as such will be much slimmer than 5cm (somewhere between 1 or 2 cm).

When I have purchased multiple PCBs off of eBay or similar, they often come attached with 'V' groove routing and you can just snap one off. Is this something that these cheap PCB houses offer, bearing in mind they probably use it to separate different boards in an order anyways? Or, if not, is there any other kind of routing they offer which would work in this scenario?

Could I arrange my Eagle file so that it had 3 copies of the board with the 'v' routing separating each board, send the relevant files off and then get 10x3 boards back ready to snap apart myself? It seems like bad value for money (although obviously good value overall) when I am paying for 5x5 cm but only using 1x5.


texts:
So I was wondering how it would be possible to design an IR remote that consists of four buttons for each channel powered by a battery. How would I be able set something like this: The receiver will have a relay that either stays always on, automatic mode with a timer for 1h30, manual 1h30, manual 12h.

Button 1: Toggle on/off
Button 2: Automatic mode. If detected reflection, turn on for 1h30
Button 3: 1h30 mode
Button 4: 12h mode

For the transmitter I know the common IR frequency is 36Khz and receiver would be a TSOP38236


texts: How I can set up a transfer function of y = mx+c?

texts:
I have a system governed by the following relationship:

\$V_{OUT} = m * I_{IN} + 5\$

I need to write a transfer function for the equation. Would anyone please give me some suggestion of how to handle the constant term?


texts: Are there any metastability issues with microcontroller SPI slave ports that can operate during sleep?

texts:
If one is using SPI to interface two microcontrollers that may spend much of their time sleeping, and if the SPI slave port is supposed to wake up its controller when data is received, that would suggest that the SPI clock wire should not be synchronized to the latter microcontroller's clock.  If indeed the clock and processor's clock are asynchronous, that would seem to imply that data written by the microcontroller to its slave port can neither be double-synchronized to the SPI clock [since it must be available to the SPI master on the next SPI clock cycle], nor can it be guaranteed to occur at any moment other than an SPI clock edge [since the SPI slave has no idea when that will be].  The SPI port on e.g. the Freescale KL25 series specifies that if a data underrun occurs, the port will output the previous data, and the next data written by the controller will be transmitted after the repeated data byte.  Putting all those conditions together would sound like a recipe for potential metastability issues if the master starts trying to read a byte just as the slave micro is writing it.

I don't know that it would be possible to design an SPI slave port which could guarantee that it would always either repeat a data byte and then put a new byte after it, or else transmit the new byte directly.  What can or do SPI slave port designs do to minimize such issues, and what can software in the master or slave do to ensure that they don't cause trouble?


texts: LQFP vs WLCSP a question about package methods

texts:
first of all, I do not have proper knowledge about the packaging methods so I am sorry If I ask more questions after your replies. I am in a model rocket project and trying to choose a microprocessor for the rocket. But I am having trouble while deciding about the package type and the pins(which is another subject that I am not sure which type I should choose). The company that I am trying to buy a processor offers different kinds of variations of one processor model. One option varies in the package type as LQFP and WLCSP. In addition to package type, they also mentioned pins such as 64-pin 72-pin 81-pin 100-pin, etc.
Now, I searched the internet for what exactly LQFP and WLCSP, learned about them. But the problem is that I cannot find information about which one of them should be used in the field rockets, or which one would be easier to assemble. These questions are also valid for pin options. I know what a pin is physically but do not know how can its amount affect the project.
If there was a chance for anyone to enlighten me about these topics, it would be marvelous. It should not have to be too specific.


texts: Deciphering which COB LED used in a circuit

texts:
I have two lamps with identical LED circuits. The lamps sometimes blink when turning on. One of the lamps already has a blown COB LED. I suspect the wiring was done wrong. I've opened it up, but I still don't fully understand what I'm measuring and seeing.

The output driver is a constant 300ma current with a voltage range of 24-36 volts. The measured voltage on the working lamp using a multimeter is 37.5 volts (measured between the + and - terminals of both COB LEDs). That explains the blinking as the output driver is turning off due to over-voltage.

What I can't figure out is why I'm measuring 37.5 considering that the output driver should drive 300mA (not measured). The circuit is the output driver with a single black & red set of wires. I believe the COB LEDs are hooked up in parallel.

The output driver is: 120v AC .15A 60Hz, output is 300mA, 24-36v.
The COB LEDs are Edison, and I believe it is either of these (based on some identifying marks):
http://www.edison-opto.com/en/product/edipower_v_he_series
http://www.edison-opto.com/en/product/edipower_v_hm_series

There are 13 visible LEDs on each COB, so I believe they are the first grouping of LEDs with these specs:
Absolute Max Ratings 6.75W (input power), 180mA (dc forward current) - this leads me to believe max voltage is 37.5v. And therefore the resistance is 208 ohms.
One of the LED types has forward current as 90mA, and forward voltage as (32.1, 34.9, 37.7).
The other has forward current as 90mA, and forward voltage as (31.2, 34, 36.8).
But with these numbers I still can't figure out why I'm measuring 37.5 across both LEDs. I would expect that the resistance is half of 208 ohms which is 104 ohms. But at 104 ohms with a current driver of 300ma (constant current of output driver), shouldn't the voltage be: 31.2?

It makes me wonder if my assumption of 300mA is wrong - even though the output driver is a constant current output driver.


texts: Detect 10V...To.. 260V AC/DC with HCPL-3700

texts:
I want to detect voltage between 10V and 260V AC / DC, I have thought to use the HCPL-3700 but if I put the 47k resistors the output is activated, but if I apply 12V the output is not activated.

Does anyone know if it can be done with this chip, or does this one not work and I have to use another type?
Basically I want to activate a 5Vdc PIC with whatever voltage is applied. I don't need zero crossings or anything special, only that it be activated with that input voltage range.
Any ideas?


texts: I came across several circuit diagram which make  use of op amplifier. What confused me is that in the diagram, there's a basic diagram of an amplifier followed by e.g 1/4 AD8662 (4 of those diagrams). Does that mean the amplifier has 4 channels or does it mean there are 4 physical amplifiers in the circuit?


texts: Surge protection for control and instrumentation signals (C&I)

texts:
While studying Weidmuller's surge protection catalogue for control and instrumentation signals, I got really confused so that I can't easily explain my question.Is surge protection for analogue signals different from binary signals?Is surge protection for such signals different from the surge protection for power supplies?
I can't understand the need for separating analogue and digital signals in surge protection application, and also seperating control signals and power signals!


texts: AC overvoltage protection for bike dynamo (alternator)

texts:
I built my own MOSFET active rectifier and DC/DC stepdown for a bike dynamo hub and wanted to use it for charging a mobile phone.
The circuit is working, but there is one thing which needs to be solved better.
When USB output (5V) is not connected to the load and I'm riding too fast (downhill 70km/h) the dynamo (alternator) produces overvoltage, e.g. 100 V. That overvoltage is transformed to heat in the transil. It is too much heat and the SMD transil was desoldered from the PCB, then all my electrolytic capacitors exploded.
Does anybody have a better solution for overvoltage protection on AC side (sine wave) voltage? It can disconnect circuit from dynamo if necessary, or just limit the voltage.


texts: I read that in transfer characteristics of JFET, Vds is kept constant and Vgs is varied. But when Vp for any device is constant and Vds is also constant then even Vgs should be constant.


texts:
For my final project, we are building an ultrasound range finder, without using a microcontroller. I have been able to build a block diagram (attached document). In the circuit, I'm using a 555 timer to modulate the output signal for the transducer, and another 555 timers to control the 4-bit counters.
How do I trigger both of the 555 timers at the same time, and stop the second 555 timer when a signal is received by the ultrasound receiver?


texts: Raspberry Pi controlling DC motor with 2N2222A

texts:
I'm new with the RasPi and I'm trying to build an automated irrigation system. The code is ok because it does what I want, it takes measurements of water content and when it's low, it changes one output (the one going to the DC motor) to High. I'm following this schematic:

Motor driver using only a 2N2222 transistor?

Same connection but using a 2N2222A transistor, 1k resistor and 1N4007 diode and a 3V DC hobby motor - not this one but close:

Source

Connecting the motor directly to the 3V power supply consumes 180mA, and the hFE of the transistor is about 150, so I calculated that the RasPi needs to output about 1.2mA to the transistor base.

The problem here is that the motor does not spin at all, with this setup my meter reads 180mA between the power supply + and the diode, and 0.2V between the motor leads.

What am I doing wrong? I also have to say that the transistor gets hot.

Thanks in advance!


texts: Changing fan Speed of a 4pin PC case fan with a microcontroller

texts:
I'm very new to electronic projects, I know the BASICS of circuits (i.e Ohms law, capacitance)but I've never constructed something on my own.

For my project I want to take the side fan for my computer case, which is a 4-pin connection to the power supply, and which also powers an LED on the fan, and interface it with a micro-controller to change fan speed based on temperature and and also user input, so it has the fan speed increases from the user pressing a button or from automatic temperature readings and a strip of LED's to light up in a row, like a progress bar to show fan speed "intensity".

With my basic knowledge I've come up with some questions that I THINK would need to be answered to do this project. As far as I know, fan speeds can be manipulated by a changing voltage, so I'm ASSUMING that I need to build a circuit of resistors that can change this output voltage value based on switches that are turned on by the micro controller, is this correct? And I'm trying to find a way that I can interface the 4-pin connection with my micro-controller? Also what kind of battery or powersupply do I need to power this circuit? Do I need to know the wattage needed for the fan? Thanks to anyone who lends me advice, It's much appreciated.

Here is the board specifications if needed http://www.socialledge.com/sjsu/index.php?title=SJ_One_Board

And a link to the fan being used. http://azzatek.com/PDF/CSAZ-1000-Solano-Users-manual.pdf (fan on the side)


texts:
I cannot seem to find any information for this diode, or for the package.  It is slightly bigger than a mini-MELF and has a repeating number 3 as cathode band. It meters like a normal silicon diode.

Any help would be much appreciated.


texts: How to use USB 3.0 inner cables by color?

texts:
I have an USB 3.0 cable I want to use only for powering a basic circuit with 5V and the max current I can get from USB 3.0.
Once cut, I can see these cables :

I know the red and black are power and ground, white and green are for USB 2.0 data.
According to these links, I can see that the 2 other are said to be SDP/SSTX/SSRX/USB 3.0 signal...
https://www.conec.com/wp-content/uploads/sites/2/2017/09/IP67-USB3.0-Assembly-Instructions-Aug-21-2017.pdf
https://www.semanticscholar.org/paper/USB-3.0-machine-vision-camera-hardware-design-and-Zhuang/da035ac587250936a1a6606ba05a2a879cc855a6/figure/3
https://www.dhresource.com/0x0/f2/albu/g7/M00/91/E0/rBVaSVsPJeiASxomAAG91UKxjdw068.jpg
But I'm not sure to understand what these are for...
My question is : are the red and black wires the right and only ones for power lines, or are there other cables that manage power ?


texts: Flipped length and Z-matched lines. How to pcb patch?

texts: I think the title says it all. I accidentally flipped the P and N lines downstream of a CSI/MIPI retimer (they are impedance and length matched). Is there any way at all to patch this on the pcb?


texts: Can one be electrocuted when cleaning a light switch?

texts:
Light switches are allegedly some of the dirtiest spots in a house, and cleaning them is recommended in many articles. However the safety angle doesn't seem to get coevered. The only thing I could find was some Australian work safety presentation which states:

do not touch with wet hands
pay attention to wet cleaning

What about wet feet? And pay attention to what, exactly? All disinfectants I know are "wet".
Should I just skip cleaning them?
Or maybe shut down the power in my apartment before (seems a bit extreme)?
Or maybe I could use some brush with an isolating handle?
I guess these questions stand for other switches as well (say, water heater ).


texts: Power meter current transformer: possible to sum mutiple phases

texts:
I am currently looking at this inexpensive power meter modules with TTL interface.

It seems to use internally the same ASIC as many chinese wall-wart power meters: It comes with a current transformer for measuring the current through a live wire and has connections for sampling the voltage on the wire.

My question now is this:
Assuming I have a 3-phase AC setup, can I thread all three live phases (i.e. shifted 120° relative to each other) through the current transformer to measure the sum of the POWER in all three phases?

My hunch is that this will not work. My primary concern is that the voltage on only a single phase will be sampled while the current transformer sees the current on three phases which will make calculating the power difficult. Also I believe on AC the direction of the current in the three phases will generally not be aligned leading to cancellations.

Is this correct?

Edit 1:
Clarification. I am not attempting to measure a 3-phase load but multiple single-phase loads attached to the three phases. The return current goes through neutral.


texts: Is the V_t in this document regular Thermal voltage?

texts:
I have been looking at this short document.

https://pdfs.semanticscholar.org/c490/4c04a7be1d675e360409178da71a1253f6d8.pdf

It uses V_t and defines it as thermal voltage of a transistor.

It does not make so much sense to me though, as input to such a filter will be audio peak values of +-0.9V. And that input is fed into a tanh() function wherein its divided by 2*V_t, so if V_t is 0.026V it like multiplying it with 19.23 before taking tanh() of it. That will completely saturate the tanh() function, and no good audio will come out. See equation 13 for that.

So is the paper using a different definition of V_t in this paper?

PS: Sorry for posting this here, but I think this is an electronics question more than a DSP question.


texts: Eagle: Remove some text of a component label

texts:
I routed a small board that will get connected to a BeagleBone Black using two 8x2 pin header connectors.

As you can see on the picture there's two labels that are drawn out of the board layout so when I upload the board on OshPark the board is bigger that what it should be.

How can I remove those two circled labels without editing the eagle component library?

Do I have to generate my own gerber files and don't use the OshPark's website to generate them?

I'm new to eagle.


texts:
I've made an amplifier from a circuit I found on the internet (below, link). I made it more or less exactly as described (same components, big heat sinks) and it seems to work great (can run at a loud volume for extended periods of time). Sometimes, however, for no apparent reason, the fuses blow and the MOSFETs have become completely conducting. I understand this can happen if a high (> 20V) voltage is applied to the MOSFET gate. No other component is damaged.

I've completely re-made the circuit about 6 times and it always happens on the same channel. The amplifier attached to the other channel might last for weeks, until I test it on the bad channel, then it breaks within a day or two. So I think what's happening is that one channel of the sound source (a cheap bluetooth receiver powered by a questionable 5V supply) occasionally has short voltage spikes, causing an over-voltage on the MOSFET gates and breaking them.

I know I could get a better source, but I want to make the amplifier better. So my questions are:

Is this a plausible diagnosis?
If yes, what can I do to make this circuit more robust against a "bad" input?

My first idea is to put Zener diodes between the gate and source of the MOSFETs (say 15V threshold diodes, the gate voltage should never get close to that during normal operation). Is this a bad idea? Or is there something else I could do?


texts: Could you help me derive this transfer function for this OP-Amp circuit, I keep trying different methods and get no where close!


texts: little endian processor and big endian processor - save number to memory

texts:
Processor save 32 bits number(123456780)_8 at address 1000.  We would like to know what values are under addresses 1000 and 10001.
a. little endian processor
b. big endian processor

First of all we must convert number to 16: 0029CBB8.
a.
1000:29 00
1001:B8 CB

b.
1000:00 29
1001:CB B8

Tell me please, if I am right ? If not, where I am wrong ?


texts: How can I decrease a DC voltage without a resistor

texts: I would like to light up a 2 W LED with a 3.7 V power source in the most efficient way possible. The Vf of the LED is 2.4 V. Is there any way I can reduce the voltage to 2.4 V from 3.7 V without using resistors as with a required current of 350 mA, the power wasted as heat in the resistor is too high. I am looking to find an easy way of accomplishing this as the circuit has to be used in a low cost device that needs to be efficient and cheap.


texts:
I need to drive 2 MG996R Servos and a MP3-TF-16P with 2 3W speakers with a Wemos D1 mini.
It works, but the Wemos is getting hot. I supose that the fuse on the +5V pin that is powering everything is warming up. can i simply bypass the fuse and the diode? What are the downsides?


texts: Finds effective resistance in circuit (no voltage source)

texts: Find the Rin, that is the resistance as "seen" by the points designated with the >> symbol. (Also, can smn explain how KVL still works in this case? Thanks)


texts: Antenna Parallel to High Voltage Line Has AC Current - Is It Acting as an Inductor?

texts: I'm attempting to use one of the roofline gutters on my house as a "longwire" antenna.  The center conductor of my coax cable connects to the gutter, the shield conductor to a grounding rod.  The gutter is near the same height, parallel to, and roughly fifty feet from a high voltage transmission line.  When I was putting a connector on the transmitter side of the cable, I was suprized to receive small shocks, like static electricity.  My multimeter shows fluctuating voltage when I measure between the two cable conductors, with a peak around 65 VAC.  Is it possible that my gutter is within the electromagnetic field of the power line and is acting as an inductor?  If so, any suggestions on how to minimize the effect to still use it as an antenna?


texts: Is it possible to have Altium ignore one schematic in a project?

texts: I would like to start using Altium to simulate parts of my schematic, but I would much rather have a separate "simulation schematic" inside the project which should be annotated  and compiled independently to the rest of the schematic sheets inside the project, Is that possible ?


texts: May I please have help calculating the noise bandwidth for the circuit below

texts:
I am trying to calculate the noise bandwidth for the circuit below. This question and diagram is taken from the book "Low-noise electronic system design" by C.D. Motchenbacher and J.A. Connelly (if anyone knows of a solution manual for this book I would be eternally grateful).

To begin this problem I know that I need the transfer function (I hope I got this part right at least).

$$H(s)=\frac{100RCs}{(1+RCs)(1+RCs)}$$
After using the information from the circuit diagram to simplify the transfer function I have the equation:
$$H(s)=\frac{100s}{(1+s)(1+s)}$$
To actually determine the noise bandwidth I need to use the formula:

$$\Delta f=\frac{1}{H_{max}^2}\int_{0}^{\infty}|H(f)|^2\;df$$

From what I read in the text book I understand that to get from a function of s to a function of f I should substitute some sort of pole but I am not sure what it should look like. The examples in the textbook are of simpler cases like first/second order low pass filters where using the relationship \$RC=\frac{1}{2\pi f_c}\$ and substituting a pole \$s=j\omega\$ results in a nice function of f, and determining the square magnitude of that transfer function is simple. However, that made sense to me because those filters have one corner frequency but a bandpass filter like the circuit below has two. Every substitution I can think of ends up with a really nasty function that I can't integrate. I know I am missing something fundamental but I just don't see it.

I guess what I would really like is guidance on how to determine |H(f)|^2 for circuits like this.

simulate this circuit – Schematic created using CircuitLab

Thank you in advance to anyone who is willing to assist me.


texts: A couple of questions about memory gates

texts:
Let's assume I have a memory block here, I didn't set any value to it, what value would it output?
If two outputs from two different bytes meet in the same wires, what happens? I'll give an example: Byte 1: 0101 0100 Byte 2: 1001 0111
Look at the following bus:

(R1 through R5 are registers, s = set, e = enable)

Let's say we have set the enable of both R1 and R2 to 1, will the two bytes from R1 and R2 meet in the same wires? (Look at my question no.2)

Couple of notes:

This is not homework, I've been reading a book about this subject and it didn't explain that stuff.
I couldn't find anything else that explains this stuff.
I know it is suggested to divide my question into 3 questions, but since each one of them is very simple enough and each of them depends on the other questions I didn't see how to do it,


texts: How do I identify a step up or step down transformer?

texts:
I have collected a big transformer from old UPS. I don't know this is step up or step down. I want to use it as step down transformer.
One side has many 5 pairs of cable and another side has 3 cables. I want to convert 220V AC to 3-12V DC.

Edit (added photo)

I have attached photo of the transformer.


texts:
My goal is to have a 7 segment display display the number from 0 to 3 in sequence and to repeat the cycle.

I have a 555 timer feeding into a 7474 (dual d flip flop) whose Q1 and Q2 outputs are giving me: {00, 01, 10, 11}.

I hooked this up to a 7447 bcd decoder that is feeding a common anode 7 segment display.

Anyhow, the display is changing but it is producing some funny symbols.

The 7 segment display is common anode and the model is ECG 3052. Here is some information on it:

I hooked up the 7447 like this:

Now, there are 2 things to mention:

I'm not using the C and D inputs on the 7447. To avoid floating inputs, do I used pull up/down resistors?
There are 2 common anodes on the ECG 3052. Can I use one and ignore the other? Do I tie it off somewhere? What about the pins I'm not using (like the decimal point)?

If someone could help me understand how to connect the 7 segment display I'd be very appreciative.

Like I said, my goal is to have the display show 0 o 3 in sequence then repeat itself.

Kindly,


texts:
I am currently having an issue with DO's on an Arduino in a constant state of high with a pull down resistor attached to a ground plane. Voltage being measured on the DO is 3v. Pull down resistor is 2.2kohm. Below is the wiring diagram of the entire circuit. Looking for suggestions on where I went wrong with this or possible solutions. Currently was thinking of either using a larger resistor array or putting a diode between the resistors and ground plane.

This is my first big project with the Arduino so any feedback is appreciated.


texts:
I would like to waterproof an FR4 circuit board that has no external connectivity requirements other than permanently attached USB cable, but it does have a number of SMD LEDs that must show. Most significant other components are an TSSOP20 MSP430 microcontroller and an LM4970. Power is via a small rechargable 3.7 volt LiPo battery.

Also, the board is to be fitted in a shoe heel(!), so adding an additional waterproof enclosure is not feasible. The water exposure is essentially moisture build-up, not actual soaking (hopefully). The device needs to last just a few months to a year.

What are my options and and what problems would I face?

If I use potting epoxy, will there be heat build-up?
If I simply use a see-through latex balloon will that survive circuit board heat?

Is there any additional detail I could add to make this question clearer?


texts: Does this design smell bad? Can I pull a pin simultaneously down and up?

texts:
I am building a simple circuit using PT7C4511 PLL Clock Multiplier. This chip has an OE pin that stops the output when LOW. By default (with no external signal driving it) it stays HIGH because of a built-in pull-up (270K).

What I want to do is to turn on and off the chip's output using a 2-pin header. However, I want it to be working when the header is shorted, and stop the output otherwise. To achieve this, I have connected 40K pull-down to OE pin, strong enough to overcome the internal pull-up, but not too strong, so that when OE is shorted to VCC, the pin can easily go HIGH again.

I showed this to a friend with more experience in EE and while he agreed that it should work, he wasn't too excited about the design. He could not point to a specific issue, but the whole thing "smelled" to him.

Is he right? Why?


texts: Using an MCP73831 charge controller with a BAS3007A Low VF Schottky Diode Array

texts:
I'm working on a design that uses a custom USB charging cable that can be inserted into the device with either polarity. The +5V is rectified using a BAS3007A Low VF Schottky Diode Array. This is then fed into an MCP73831 charge controller.
The issue I'm facing is that, due to the diode drop across the rectifier, the charge controller terminates charging before the battery is completely charged.

During charging I am measuring +4.36V on the output of the BAS3007A (net label: USB). Just before the controller switches to constant voltage charging, the current consumption drops to ~10mA with the status pin of the MCP73831 toggling on/off at about 1kHz.
If I apply a voltage of >4.5V after the rectifier, the same battery will resume drawing 200mA and the status pin will stay low until the charge sequence terminates as expected.
I believe it is because of this statement from the MCP73831 datasheet shown here:

Any thoughts on how to fix this? Any other charge controllers to recommend that will function with this low of an input voltage? Should I consider boosting the rectified voltage back up to +5V?


texts:
Below are the output characteristics of a common emitter n-p-n transistor:

I need to know why collector current becomes independent of the collector-emitter voltage after some time? I don't exactly know the reason.. I tried a lot but failed... Web didn't helped me. Kindly help

Also, why the constancy appears at higher collector emitter voltage as the base current increases?


texts:
I am working on this small project getting a relay to turn on/off the amp. when it gets a 12 V trigger from a netstreamer.

The relay is powered from 5 V USB 230 V adapter.

Question: should I connect the ground, -12 V, to the same ground as the 5 V power supplier?

EDIT
https://www.electrokit.com/uploads/productfile/41015/41015704_-_5V_Relay_Module.pdf


texts:
I have a question regarding RS232 communication between a VectorNav VN-100 Gyro, Mbed LPC1968 uC and PC. I am using gyro to measure the number of rotation and processing it in the uC and displaying the number of rotation on a seven segment display. here is the top level diagram of the system (please ignore the power distribution, it uses a inbuilt battery)

All the electronics are inside a steel container, so what I want to do is to be able to reach gyro through the connector to send various commands. Since, gyro is already connected (tx, Rx) to uC how can I connect it to the connector? Here is the pin out of the gyro,

Pin 2 and 3 are connected to uC so can I use pin 8 and 9 with MAX232 in order to connect the gyro to the PC?

[Updated to include model numbers of Gyro and MCU]


texts:
In general, there are many ways for DC-DC conversion: SMPS, charge pump, linear regulators, zenner diodes, even resistive dividers. But lets say I want to create 2 voltage rails, +Vcc and -Vcc.

I can use an explicit negative voltage converter like an inverting charge pump or a buck-boost inverting topology converter, or even build a dual PSU that produces 2 rails centered around earth.

Can I achieve the same by just have 2 DC-DC converters, calling the middle node GND, and calling the low voltage -Vcc and the high voltage +Vcc? Are there any downsides to this method rather than using an already established GND and pulling a rail down with reference to that, aside from potential shorting risks to earth?


texts: What happens between the pinch-off point and the drain?

texts:
The typical picture from the pich-off phenomenom assumes that when channel pich-off occurs the density of mobile charge in the region from the pinch-off point up to the drain becomes zero.
This regions is asumed fully depleted and there is present an electric field which sweeps off all the charge that it is injected in this region. In other words, although the density of mobile charge is zero, current can flow through the depletion region.
My question is related to this last specific statement. If the charge density is null, the drift density current is also null by definition since, for intance for a NMOS, the current density  Jn = q n mhu E. Obviously, this cannot happens. In this sense, my questions are:

How this effect can be interpretated?
Which charge density supports the drift current?

I have been cosulting several books on the topic, but all of them omit this comment. Maybe is trivial, but any ligh on the topic would be welcome.
The question can be also translated to current flow through the depletion region in diodes.
Regards,
Antonio


texts: Voltage Drop Across MOSFET in Ground path

texts:
I have an arrangement in which an NMOS is connected in the ground path to control the power flow as shown below :-

When the FET is on , current will flow & there has to be voltage drop across the mosfet. Because it is connected on 0V already, how to analyze the voltage drop across it?


texts: Reliability of Serial IO Expander like MCP23S17

texts:
Background:

I am doing a re-design of an existing system moving from HC11 base with memory mapped I/O to an ARM Cortex-M3 with serial SPI/I2C I/O (opto-isolated inputs and relay outputs).  I/O access will be via serial SPI or I2C to I/O expander chips (MCP23S17). 2 Chips per board for 32 I/O points each, and up to 4 boards can be stacked/interconnected via short ribbon cable for the SPI buss. The microprocessor board will be stacked on top of the main I/O board and have access to additional I/O boards via the SPI buss as mentioned above.

Question:

Is going this serial route, SPI to MCP23S17, going to be rock solid reliable in accessing the I/O points or will the serial nature just be too susceptible to noise and/or other related problems?

This is mission-critical control system running 24/7 7 days a week, polling the I/O say between 500Hz and 1kHz. I want the SPI bus speed to be around 2MHz, so not all that fast but also not slow.

In 20+ years with my current HC11 memory mapped design with the I/O being accessed over a 3ft 50pin ribbon cable, I have never had a single issue but I am concerned that moving to a serial SPI-based design could start causing all sorts of problems.

Would appreciate any of your thoughts and experience with this.


texts:
Do rotary incremental encoders exist that have the smooth feeling, as if turning a  potentiometer? If so, does this have a name, how to identify these?

I love the flexibility of encoders in my designs, but I don't like the clunky feeling. Disclaimer: my experience is limited to two cheap encoders of Aliexpress ;-)


texts:
I am a student now currently learning about interfacing 8255 with 8086. For me the doubt is that,
is there a need for external i/o interfacing like in 8086 for latest processors? what is GPIO ?


texts: I need help with this problem. The transfer function that I found is ((RCS+1)/(2RCS+1)) , but then I cannot go further because the form of T.S is untypical. The typical form of this question is RC filter for which the transfer function is (1/(1+RCS)), but adding a resistor makes that complicated.


texts: Reducing the memory address bus by adding banks

texts: If you are trying to control memory from a CPU, then if you use two banks instead of one, you can remove the first address line. If you use four banks, then you can also remove the second as well. Why is this?


texts: IGBT SOA rating vs. Short Circuit rating

texts:
I have an IGBT (with integrated anti-parallel diode; forgive the BJT symbol in the diagram) that is switching an inductive load with a ~300 Vdc supply. The threshold voltage is ~5V and I'm driving it with 0-10 V PWM pulses.

When I short the load to stress test, the PWM pulses the IGBT gate for a few cycles (before the micro catches the event). I see a large collector current spike for a few microseconds (~70 A for ~2 µs) that corresponds to the first PWM pulse after the load short event, followed by a few more similar pulses with much lower peak currents (~25 A for ~2 µs) before the micro turns off PWM.

Two questions:
1) Am I exceeding the IGBT current/SOA ratings? The IGBT has a short circuit rating of 10 µs at 360 Vcc, and a SOA max current (at any Vce) of 55 A. Is my 70 A spike going to damage the part? A load short isn't something I expect to happen very often, and I don't know if I need to be worried about this happening as a one-time thing.

2) After the load is shorted and the PWM is still firing for a few pulses, Vce stays at around 300 Vdc even though I'm seeing current flow with each of these PWM pulses; it's like the IGBT is on (passing high current) and off (Vce doesn't collapse) simultaneously. Even if this current was being delivered by the cap, shouldn't I see Vce collapse?

Thanks for your input.


texts: How to find the RMS value of a sine wave with DC offset and retain the negative sign

texts:
I'm trying to build a Quadrature setup where an input signal is mixed with a reference signal that is in-phase and another one out-of-phase by 90deg.

The idea is to extract the real and imaginary amplitudes (magnitude and phase) in a signal produced by an impedance when excited with the reference signal.

However, I'm trying to get around having to sample both of the mixed signals using an ADC and then extract the data - due to sampling rate limitations.

To enable this, I'm trying to use an AC-TrueRMS converter (AD8436BRQZ) that would produce the RMS equivalent DC signal.

However, I want to retain the negative sign, if the signal for example is fully negative (i.e. with a DC offset).

Is converting to RMS not the right approach?

Thanks


texts: Connecting 12v Parallel LED Series to Arduino

texts:
I want to connect my 12v LED circuit powered by an external 12v adapter to my Arduino so I could control the LEDs

First, I'm a beginner in Arduino and have little knowledge on electronics. I know that my Arduino Uno can only support 5v and 400mA. I could have easily connected my circuit to it but I'm using 80 LED with a total of 1600mA. As a resort, I found this design (for 50x 2.2v LED just a part of the 80 LED circuit).

Is there a way for me to hook up the 12v circuit to Arduino so that I can control the LEDs? Any ideas? Suggestion?


texts: Heinner OMX-600 blender motor not turning

texts:
I have this blender that won't spin when switched on, the leds turn on tough.

I managed to take it apart:https://imgur.com/a/eMSSXm4

From the mains power (!caution is used all times!) we have:

on line going to a micro-switch that I shunted (it's purpuse is to make sure the bowl is secure on top of the blender).
a main PCB that has a few resistors,  cap (0.1uF),  triac (BTB06) ,  diode (DB3), turn knob ( has 7 states: off, CCW - pulse (has spring and turns back to off if let go) + 5 speeds (all CW) )
a secondary PCB that has 3 LEDs, 2 resistors and an IC that seems to read MDD M7
motor

My theoretical and practical background is limited to low voltage DC circuits mostly but I do understand the dangers of working with mains voltage and would like to further expand my knowledge in this area.

I was thinking of first ruling out that the motor is not faulty. Where should I probe with my DMM on it? Should I be measuring continuity(resistance) along the coils or try to measure AC with it ON as so to make sure it's getting power? ( Yes, dangerous if not careful)

Is there an practical way to test that the triac or diode ( based on the datasheet I see it's not a simple zener diode ) is ok?

Taking parts off the PCB is not an issue if there is a test rig I can create to make sure components are not faulty. I also have an oscope if there is a need for it.

Thanks!

Later edit:

I was lucky and managed to get locally a DB3 diac and a BTB12 triac (i'm guessing the higher amp rating shouldn't influence negatively). After soldering them on there was no change, no motor spin.

I managed to get my hand on an identical, working blender.  I then cut the wires from it's controller and hooked it up to my motor and there was a small buzzing from the PCB but no motor spin (I only had it on for max 2 sec as i didn't want to burn anything ). When I hooked up the controller that I am reparing to the working blenders motor it spun up and worked normally. This way I was able to pinpoint that it's my motor that is faulty.

After a little research I found out that it's a universal motor and thus can be powered with my DC bench supply (something i'm more familiar with :P).

If I hooked my bench supply's leads (polarity didn't matter) to:

White lead and brush guide closest to me ( 1 and 2 pic ) the motor would spin.

White lead and brush guide furthest to me it would arc (short).

Blue lead and either brush guide nothing would happen.

Pictures: https://imgur.com/a/k10ZRRw

Am I safe to assume that the stator winding that is on the blue side lead has failed?

If so, what are my options?

Thanks


texts:
I am working with an ARM Cortex M3 chip (reference manual available here). I'm trying to get the baud rate of my USART communications right. Reading pages 613 onwards, I understand that the value I should set for USARTDIV depends on the clock rate of AHB1 (since I am working with USART3, governed by the AHB1 clock).

Looking at pages 614 onwards, I see that the clock rate f_PCLK can take many different values (8MHz, 12Mhz, etc.). However, I cannot see anywhere where I can set the speed of that clock.

How can I measure/change/read the speak of the AHB1 clock?


texts: noTone() and tone() are not implemented for the Arduino Due

texts:
As it turns out, noTone() and tone() are in the core arduino API, but seemingly not implemented for the Arduino Due.  I was hoping to use tone() and noTone() to implement the mario death sound found here, but when I add the code and compile it, I get the following errors:

trenchRun:154: error: 'tone' was not declared in this scope
trenchRun:156: error: 'noTone' was not declared in this scope

In case you're interested, here's an SSCCE, compiled against Arduino 1.5.4 on Mac OS X 10.8:

void setup() {
  // put your setup code here, to run once:
}

void loop() {
  tone(1, 12345, 1000);
}

sketch_oct24a.ino: In function 'void loop()':
sketch_oct24a:7: error: 'tone' was not declared in this scope

Since I have an Arduino Due, I am limited in using Arduino 1.5.4.

How do I implement the tone() and noTone() functions for the Due?


texts: How much energy is wasted by plugging a laptop wall charger into an automotive inverter

texts: I've been plugging my laptop into an inverter, from my van battery, the adapter is 60W, but it seems strange to convert DC to AC and then back to DC again. The inverter is 700W. How much energy am I wasting by converting from DC ti AC and back.


texts: Is it a problem in a single-phase system, if a generator shares neutral with the grid?

texts:
I'm planning to use a generator to bridge longer power outages. Both the house and the generator are single-phase. If the main breaker is off, it will only disconnect the phase, the neutral will still be connected to the grid. Now if a generator is added, it would share neutral with the power grid. Is that a problem?

Disclaimer: I'm aware of all the other risks involved. The generator will only have 2KW, all bigger sinks will be unplugged prior, the circuit used for the feed supports 10A @ 230V and already hosts most of the devices that need powering.


texts: How to create a square wave signal with 120MHz

texts:
What is a cheap way to generate a square wave with a frequency of 120MHz. I've been thinking of the following solutions:

Use a Raspberry Pi, then use a timer or something from that board
Use an oscillator (will the signal be a square wave or sinusoidal?)
Use an oscillator + PLL
Use an FPGA/CPLD

I like the oscillator (e.g. http://at.farnell.com/saronix/s1903c-120-00-e/quarzoszillator-smd-120-000000mhz/dp/1210018) approach very much, but I couldn't find out if the output signal will be a square wave or sinusoidal.

I need the signal to feed it into a SerDes part and then do some tests with that part.

Any ideas?

Maybe I should add that the device will not be directly placed near the IC, therefore the signal should have some "power" on its output line.


texts: Multiply 4 Digit Binary Number By 3 - Circuit

texts:
I want to find a way to multiply a 4 digit binary number by 3.

I have this circuit that doing this process and I don't understand how it works.

To multiply a number by 2 I need to shift the digits to the left and if I want to multiply by 3 I will have to shift it by and then add the original number

I would like to get some explanation how its doing the process I wrote before.


texts: Auxiliary contacts on contactor to power solenoid valve

texts:
I'm just trying to introduce cold water in to industrial shredder.
Connected cold water supply to machine. That's not good because when I  forget to turn off water it will overflow. I have not seen whats inside machine, but I know there will be a PLC, contactors and +24V power supply.

I'm thinking to install NC solenoid valve 24 V DC and power it from auxiliary contacts on  motor contactor. Therefore water will be introduced only when the motor is running. To be more specific, there is three L1, L2, L3 and NO auxiliary contact on top and bottom sides of contactor.

I am thinking to get +24 V DC from power supply which supplies power to PLC, connect it to NO auxiliary contact on contactor, another NO auxiliary contact goes to solenoid valve, then from solenoid valve goes to 0. 0 will be on terminal block somewhere. My concern is that scheme will  be safe?

Machine operates outside, temperatures winter from -5 to summer +25.
Water will go (solenoid activated) for about 15 sec, then stop for 15 sec, then start again x4 times. Solenoid will not burn? PLC will not burn? I'm thinking to install Asco Solenoid Valve SCE238D002.24/DC, 2 port , NC, 24 V DC, 1/2 in.

Any help would be appreciated.


texts:
I have seen many of the 4,6,8...layer stack up . Layer 2 prepared as solid GND plane for shorter return current path(reference plane.

What is the reason for layer 2 is ground plane in most of the stack up instead of power plane?


texts:
What kind of components are these?

They do not have any marking, one is bigger than the other.
Both have 4 pins, and 4 coils.

They come from an old Philips CRT.


texts: I am trying to implement an add-on battery pack to a UAV for when the main battery has low voltage. The main battery in the UAV is a 6s 22.2V 30aH Li-po battery. The add on battery pack is to be determined but will be connected in parallel and with the same series cell count. I'm finding a safe way to balance the voltage of the two packs to prevent a rush of current in the lower voltage battery. Currenty, I am looking a t a simple DC-DC buck converter. Any suggestions on any other ways to do this? Thanks!


texts:
I have designed a power supply that has two outputs, one at -3kV (200mA) and one at -6kV (10mA). A new design challenge has arisen that includes the need to pulse both of the outputs from nominal load to 0A anywhere from 100Hz-100kHz with varying duty cycle. At the moment, although the primary side switches have a frequency of 300kHz, the response to the output loading is not fast enough.

I have posted in other forums and some have mentioned that high-speed linear regulators are able to negate the effects of the load transient. However no-one has been able to assist with a possible circuit for me to attempt to implement. I will attach a schematic which shows what I have so far, without any secondary side control.

I have spoken to some engineers who say that pulsing the input of a linear regulator causes the pulse to be reproduced on the output, however I haven't got much experience with linear regulators to understand what this means. I attempted to do something like this in LTSpice, which I have also attached, but the voltage stresses on the components are too severe and I don't know if this is at all on the right track. I will attach that schematic and results also.

Has anyone dealt with pulsed loads with linear regulators before? Has anyone got any advice to effectively regulate the voltage across the load when the output is pulsed in such a way?


texts: Can we think of an impedance or an admittance as a case for a transfer function?

texts:
We define impedance as the complex ratio of potential (voltage) over flow (current). We can describe it as how much a system "impedes" the flow according to a potential applied to it. But wouldn't it be better to think the other way around, as the resulting potential produced by a flow through the system?

This interpretation of impedance feels more organic with the topology of electronic systems. Once current flows through an element, it produces a voltage potential. The input is current, the output is voltage. This would turn flow into the input and potential into the output. Output/Input = Transfer Function.

This approach makes the concept of admittance, which is sometimes better applicable for mechanical systems, easier to manipulate. The input for a mechanical system is usually force and the output is velocity. Again, Output/Input = Transfer function.

I'm modelling transducers and it seems like transfer functions are a more general concept for describing the behaviour of a system that converts energy between domains (electrical<->mechanical).


texts: Improve a ECG I am using an instrumentation amplifier

texts:
I am doing an EMG as a part of my senior design project. I am currently using an Instrumentation amplifier but my professor suggested using a driven right-leg circuit. I was wondering how using a right-leg circuit would make it better (what are the benefits in filtering, speed, etc)?

He also asked me the following question: What is primary drawback to leaving a patient “floating” (i.e., not connected to the same voltage reference as the op-amp amplifier)? which I don't know how to answer. I thought that it was because the voltage difference could get dangerous, but it doesn't seem plausible.


texts:
Sadly i am not really experienced with electronics, i have recently obtained an Arduino and a motor driver and i am trying to hookup some lego motors.
My motor driver outputs 2 signals, one for direction (high/low) and one for speed (PWM).
My lego motor (Power functions medium) has 2 inputs for PWM signals, one forward and one reverse. So i was thinking i could connect these by sending my PWM signal from the motor driver to one of the two inputs based on the direction signal voltage from the motor driver.
What kind of component could do this job? I have been looking into using a transistor as a switch but i am not sure if i will be able to make it work like i want.


texts:
I have been test the example. AVR1316: Using the XMEGA Self-programming driver on ATxmega128D4 device through the Atmel Studio simulator. The program executed fine but does not modify the content of the flash section.
Eventually I figured out that the code was not uploaded to the bootloader section so I added -Wl,--section-start=.text=0x20000 to the linker flags.
The problem now is that the BOOTRST fuse is set to application reset as seen below

When I change the BOOTRST fuse to allow starting from the Boot Loader section

The changes don't persist when I exit the interface.
I don't have access to a physical device so I cannot manually modify the fuses. Is there any way to change the fuses for the simulator?
Thanks


texts:
I have a basic question regarding silicon-based MOSFETs and alternative MOSFETs such as InGaAs.

I am aware of the fundamental equations in which describe the current flow for the silicon channel MOSFET but I'm curious to know if the equations hold for InGaAs. I understand that the basic parameters will change, such as the electron mobility and the gate oxide capacitance (assuming different interfaces are used). But do the fundamental equations hold? For example, what about the equation below?

$$ I_d = \dfrac{1}{2}k'_n \dfrac{W}{L}V_{OV}^2$$

For example, if someone gave me a diagram of an InGaAs MOSFET, and told me to calculate the current through the device considering all three regions of operation (saturation, triode, subthreshold) and for both long and short channel, could I still open up any analog CMOS book, grab the equations I need and calculate which is needed?

From all the papers I've read so far, the equations seem to hold regardless of the material.


texts: How to create a dual zone microwave sensor

texts:
There are these microwave sensors in car alarms that have dual zone. This means that they can detect movement both outside (a small distance) and inside of the car.

How are they implemented?

I suspect two regular microwave sensors that have different powers: one with high power for outside detection and one with low power for inside detection only.

Thank you!

Edit: link to a dual zone microwave sensor: http://www.crutchfield.com/S-D98ka8tAZol/p_220MV3/Code-Alarm-MV3.html. It's a single unit that is mounted under the plastic of the console between the driver and the passenger seats.
https://www.youtube.com/watch?v=l7fZx1sU4_8 a quick description of how such a module is used in a car alarm.


texts:
I'm learning about op amps and I have the following problem. I need to make a circuit using one op amp that give me the following output (Vi input, Vo output)

I know that the output will be like
$$
v_o = 4\,v_i+6
$$
So I assume that I can make this work with an additive non-inverter amplifier, where one of the inputs will be the 6 V offset. I think that a configuration like this is what I need

I found that the equation for the output in this case will be this
$$
v_o=\left(\frac{R_f}{R_s}+1\right)\left(\frac{1}{R_1}+\frac{1}{R_2}\right)\left(\frac{v_i}{R_1}+\frac{V_2}{R_2}  \right)
$$
And then I played around with the resistors but I didn't reach anywhere. I dont know what I am missing


texts: Switching a relay with an Arduino using a transistor and an optocoupler

texts:
I want to switch a relay with an Arduino. The Arduino runs on 5V though, while the relay needs 12V. I want to use this circuit:

Will this work and what transistor and optocoupler do i need to use?


texts:
I was looking for a circuit to give me 1hz pulse for a digital clock and i found this circuit

Right now I have no idea how to connect potentiometer, i haven't used one before.
I'm trying to make this circuit

Where should i connect the pins in this circuit to make it work.
here's the pin guide


texts: Magnitude of \$I_{CBO}\$ in a typical transistor

texts: I read in a book that \$I_{CBO}\$ doubles for every 10 degree rise in temperature and hence contributes to thermal runaway. However I am confused since essentially it is the reverse saturation current through Base-collector junction while Emitter-Base junction is open circuited, so it should be something in μA and even if it rises 10 folds , it will still be negligible compared to other curremt changing factors so I tried to search for magnitude of this current to resolve my confusion however i was unable to find it on internet. So kindly provide the data.


texts:
Could someone explain the most important reasons for an analog designer to use MOSFET transistors in the subthreshold regime? What are the advantages and disadvantages? Generally, the circuits in mind that use transistors in their subthreshold regime should have 1) low noise 2) low power and 3) should amplify signals!!!

Note: I know that in the subthreshold regime, gm takes the maximum value for a constant bias current.

For example, in below circuit, why should we use the transistors in the subthreshold regime if we are biasing the circuit with Ibias? Why would the power consumption of this circuit be smaller if the transistors are operating in the subthreshold region? In this circuit, we have constant power supply (VDD and VSS) and constant biasing current (Ibias).


texts: Looking for a serial 9800 baud device that can input a string and output a modified string

texts:
I'm looking for a simple programmable device that has RS232 inputs and outputs that can take a string of ten numbers and output a modified string over 9800 9600  baud, 8 bits, 1 stop bit, parity: none.

For example:

input:

0123456789

output:

the+string+is+now+1234567890

I know I could do it with something like an Arduino but I am looking for something a little simpler and hopefully more reliable.


texts: Voltage drop by reference voltage generated by zener diode

texts:
I am now designing a circuit looks like this:

simulate this circuit – Schematic created using CircuitLab
My goal with this circuit is to compare the input digital signal with a reference signal generated by zener diode D1, so that the result could be identified by the differential I/O of MicroLabBox. The minimal difference between those differential ports is 100mV.
The problem is, when the input signal goes to LOW, some current must be drawn from R1 due to the diverse current flowing through Ri5, which leads to the drop of reference voltage at D1. The more input signals are referring the voltage at D1 at the same time, the more the reference voltage would drop.
Is there a solution to this problem?


texts: Wiring an optocoupler to have both inverting and non-inverting output

texts:
Can an optocoupler be wired to give both inverting and non-inverting logic output without additional active components?

I'd like to avoid using an inverter if possible, but also curious as to whether this is trivially possible.

Suppose I am talking about a normal PC817 with phototransistor output.
Also I want both outputs to be isolated.


texts: One port Vector Network Analyzer (VNA) Calibration without the given standard Calibration Kit

texts:
I am trying to do a one port VNA calibration for measuring filters at the GHz band. The VNA that I am using is Keysight E5063A. However, I am running into some conceptual as well as some practical problems. Any help will be greatly appreciated.

I do not have the calibration kit provided by Keysight. However, I am using a standard open, short, and load (50 Ohm) that I found in the lab I work in.

Details:

Open is the standard BNC Open.
Short is the standard SMA short.
Load is 50 Ohm mini circuits, operating range DC - 18 GHz, Model number: 30918.
The band at which I am calibrating is 4 GHz to 6GHz.

Procedure:

I connect a standard ST18 SMA, 36 Inch cable to port 1 of the network analyzer. The purpose of this is
to reduce mating cycles. Going into the calibration menu, select one port calibration.
I connect BNC Open, and press open calibrate. I connect Short, and press short calibrate.
I connect load, and press load calibrate, click done, and I save this calibration.

However, now when I see the results on the smith chart on the network analyzer, I do not see a dot on the edge of the smith chart for short and open. Instead, I see an arc. For the load, I see a dot. I do see open and shorts maintaining a 180 degrees phase separation throughout the 4 GHz to 6 GHz band.

Questions:

Why is the arc caused in the first place?
Is it because of fringing capacitance (inductance) for open (short)?

Can I go ahead and make measurements of filters with this calibration?

I am worried that because of this, the complicated circuit network that I am trying to measure, may not reflect its right characteristics due to calibration errors, if there are any. In such a circumstance, what can I do, to know for sure that what I am measuring is exactly what it is at this band (and there are minimal systematic errors.)


texts:
Today I purchased a USB memory card reader. I cracked it open and saw that it basically only has an AU6477CL IC, which is based on the AU6370, which is a chip which takes SD/MMC/etc pins as input and acts as a USB driver for a computer to do i/o on the card. Here is the datasheet for the AU6370.

Where can I buy one of these things? It seems like every card reader in the universe is driven by one of these ICs, but short of buying 50,000 from alibaba (maybe), I can't find them anywhere.

Alternately, does anyone know of equivalent ICs which perform similar functions? Generically, what would I be searching for?

For hobbyists, is the best option really to use an AVR/PIC to write our own code (or existing libraries) if we were to create our own memory card reader?


texts: What is this type of digits-only LCD called?

texts:
I've seen this type of LCD many times in weigh scales, calculators, gauges, micrometers, etc. I know it's a fairly traditional display but I really like its compactness, simplicity, and maybe it even costs less, versus TFTs or smartphone-type touch displays.

[What is it called? Answered by @kevlar1818 and @stevenvh: "Seven-segment display"]

I would like to work with this type of LCD, for example, I just found this 8-digit one called VIM-878  from the Digikey catalog; here is its datasheet.

How do I interface with it? I would like to know what would be a good/common way of interfacing with it from a simple AVR microcontroller like an Atmega8 -- preferably with interfacing circuitry/parts that aren't too physically large.

I presume some sort of driver or multiplexer would be necessary? I guess I'm looking for some beginning perspective from others who may have better experience interfacing with this type of LCD.


texts:
I have built a ~50W class d amplifier powered by a 12V SMPS. My problem is that the output of the SMPS has high frequency noise. I know that the noise is not audible but I would like to remove all of it, so I decided to put an input filter between the SMPS and the amplifier.

To build the input filter I made a search and found these two options:

1) Standard LC filter:

simulate this circuit – Schematic created using CircuitLab

2) Common mode choke:

simulate this circuit

I know that the first is for differential noise and the second is for common mode noise, but I don't know what is the best solution.

What is the best solution? And why?

Can you also tell me what value should the cut-off frequency have? Should it be as low as possible or should it be over the audible range?

Thank you.


texts: Negative Inductance and Cascaded DC/DC Converter Instability

texts:
I'm trying to debug a pair of cascaded DC/DC converters and have ran into a brick wall.  The local FAE said that it is probably something to do with "Negative Input Inductance" on the second converter messing up the stability of the first converter (but the FAE isn't around to "help" more).  The problem is that I can't find any app notes, papers, books, etc. on this issue.

My question is:  Do you know of any literature on such issues?  Or better yet, some ideas on things to try or look at?

Here's my setup...

Converter 1:  +4v to +12v@1 amp out boost converter.  Switching frequency is about 350 KHz.
Converter 2:  This is actually a 10-ish watt Class-D audio amp (which is basically a switching buck converter).  Switching frequency is about 310 KHz.

And the problem...

Converter 1 works fine with a resistive load instead of converter 2.  It even works if the resistor is switched in/out at audio frequencies.

Converter 2 works fine when powered from a benchtop power supply.

When Converter 1 is feeding Converter 2, C1 will shut down due to over-current through the MOSFET.  It shuts down easier if the audio frequency is lower.  Above a 1 KHz sine wave it seems to work fine.  When it shuts down, the power output is only about 50% of what the converters are able to do separately.

Ideas?  Pointers?

Update:  I found the problem.

There were two bugs...

Basically, Olin was correct.  I did a miscalculation.  The first converter should have been able to supply twice the current that it was providing.  Instead of +12v at 1A, we needed 2 amps.
Converter 1 is a current mode converter-- meaning that it has a current sense resistor between the MOSFET and GND.  It appears that the PCB traces and vias for this signal path was not up to the task.  I tried several resistors in the 4 to 24 milli-ohm range, but suspect that the traces/vias were adding another 5 or 10 mOhm.  The end result is that we were overcurrenting sooner than we wanted to.

In the debug process, I isolated Converter 1 from the rest of the circuit and tweaked it to provide a solid 2 amps into a resistor load.  Once it was solid, I connected it back up to the audio amp and it worked fine under all expected loads and audio frequencies.

So, apparently, it had nothing to do with negative inductance or whatever.

For being a mostly-digital guy, I sure am getting a lot better at analog stuff!  :)


texts: Error Correcting Code Generator Circuit Implementation with XOR gates

texts:
I am supposed to implement the logic circuit of an ECC Generator. The circuit itself has 8 Data bits (D1-D8) as inputs and as outputs it generates a 13-bit vector, which is the hamming code (with parity bits P0-P4) that protect the Data bits.

Therefore, we have:

P1 P2 D1 P3 D2 D3 D4 P4 D5 D6 D7 D8

P1 = XOR(3 5 7 9 11)

How would I implement P1 in a circuit with XOR gates to begin with?

If I feed inputs 3 5 7 9 11 into a XOR gate, will it indeed give me the result of the parity bit 1 (P1)?

This is the schema of the ECC Generator:

Thank you so much!!!


texts: How can a small device produce two million volts?

texts:
After reading a shopping magazine, one of its products featured a stun gun the size of a large wireless car door opener* with the ability to produce two million volts. How can a small device electronically produce two million volts?

*Exact dimensions are 3.65"x 1.15" x .6"

Edit: As requested, here's the product's link: http://www.heartlandamerica.com/browse/item.asp?product=keychain-stun-gun&PIN=170414&BC=S&DL=SEH1


texts: Compatibility between Arduino ADK and NFC Shield

texts:
I have an Arduino Mega2560 ref3 ADK which is connect to Android. I also have a seeed studio NFC shield connected to it.

The problem is that if I try to initialise the AndroidAccessory library and the PN532 library in the same sketch, it doesn't work. If I try to run my sketches separately it does work.

I believe that these two libraries are not compatible.

Does anyone have an idea what the problem may be?


texts:
i have a stepper motor (controlled by an arduino) that moves some gears and a pulley. the problem is that the pulley jerks a lot: the movement begin and stop too much suddenly. to make the movement more fluid i think i can use a kind of ramp: the first movement are slow, when the motors has reached the velocity it keep going on, then smoothly slow down.

i have tried to use a sine wave in this way:

// generate ramp
float t = 0;
float deltat = PI/(200+1)
for(int i=0; i<200; i++) {
    ramp[i] = 1000 - sin(t)*900;
    t += deltat;
}

now i have a ramp of 200 elements that goes from 1000 (very slow) to 100 (very fast) following a sinus wave. now i move the motor with this code:

for(int i=0; i<200; i++) {
    int delay_velocity = ramp[i];

    digitalWrite(STEP_PIN, HIGH);
    delayMicroseconds(delay_velocity);

    digitalWrite(STEP_PIN, LOW);
    delayMicroseconds(delay_velocity);
}

this works quite fine: the pulley does not jerk so much and i have control on how many steps to do.

but this work around has also problems:

i can't make ramps very long (due to overflow in atmega) - say an array no more longer than 400 elements more or less (it depends on how long is the arduino sketch)
i have control on how many steps but i have no idea on how many time it takes to get it completed (i think i can calculate it with some summation or integral but it is not so practical)

so i'm looking for some other way to smooth my movement. i think i can have a different curve instead of a sinewave. something more like this?

till now i don't have considered to generate the ramp in a computer and then pass it to arduino but could be a possibility.

some advice? thoughts?


texts: Draw state transition diagram for identifying a sequence of bits

texts:
A state transition diagram has to be drawn for the following scenario. (Later it has to be implemented using D flipflops)

Scenario:-

A sequential machine to resolve a 4-bit security code. The code is "1010" and it is sent to the resolving circuitry as a sequence of bits. The output of the detector should be raised to 1 if and only if the correct code is detected.

It says the code is sent as a sequence of bits and I tried to come up with the state transition diagram as below.

Is it correct? Or is there something missing?


texts: What should I look for in a replacement capacitor


texts: Maximal relative error on Wheatstone Bridge

texts: I just need a hint about calculating the part a. How can I deduce the values I need to take into account to calculate the maximal relative error? I guess 'x' needs to be 10, that is, the maximal value in order to obtain the maximal error.


texts: Ripple counters versus synchronous--pros, cons, and power consumption

texts:
Substantial edit--note that David Kessner's answer was written in response to the original posting; view the edit history to see what he was responding to

From what I've read of digital design, there is a very strong tendency toward the use of strictly synchronous circuits in which the only 'sequential' subsystems are flip flops which share a common clock.  Signals which cross between clock domains almost always require double synchronizers.

I've seen a number of articles that suggest that fully-asynchronous designs are very hard, and are prone to having unforeseen pitfalls.  I can certainly appreciate that if the inputs to any type of latching element have no specified timing relationship, it's mathematically impossible to absolutely guarantee anything about the output, and that even getting things to the point where odd behaviors are unlikely enough that, for practical purposes, they don't happen is often difficult without a double synchronizer.

A number of blogs also talk about the evils of gated clocks, and suggest that it is much better to feed an ungated clock to a latch along with a "latch enable" signal, than to gate the clock.  Gated clocks not only require great care in their implementation to avoid 'runt' clock pulses, but unless extreme care is taken to balance out delays, circuits operated from separately-gated clocks must be viewed as being in their own clock domain.

What I haven't seen discussed much is the notion of circuits which use sequential subsystems that aren't all triggered by the same clock, but will always be stable within a certain duration of a clock edge.  If one is trying to implement something like an N-bit event counter, having many flip flops all driven by a common clock will require, at minimum, charging and discharging the gates of 2N transistors with every clock transition.  If one were to instead use a 'ripple' arrangement for the first few stages, one could substantially reduce the frequency of signals reaching the upper stages, thus reducing current consumption.

I've seen a few processors that feature an asynchronous prescalar stage on the input of a counter, but none of the prescalars I've seen allow for the processor to read them.  Further, nearly all of the chips I've seen that have such prescalars make it impossible to write to the timer value without clearing the prescalar.  My suspicion is that on many such devices, the prescalar does not actually clock the main counter, but instead is used to determine, on any given cycle of the system clock, whether or not the counter should be advanced.  While some such systems provide a mode in which one of the counters may be set to "fully asynchronous" mode, allowing operation within sleep, it tends to avoid gaining or losing counts if one needs to use the timers for anything other than a full-period overflow and have them count consistently when switching between waking and sleeping.

It would seem that some of these problems could be eased by the use of a graycode counter, and that the implementation of such a counter could be eased by the use of a "semi-synchronous" design as described above.  It's possible to design a relatively compact and fast asynchronous bidirectional quadrature-input graycode counter which will tolerate metastability on either input as long as the other is stable (during the time one input is metastable, one output will be undefined; provided the metastable input stabilizes before the other input has a transition, the output will resolve itself to the proper state).  The outputs would not be synchronous to any particular clock, but if the inputs change on a particular clock edge, the relationship to the outputs would be predictable.  Has anyone ever heard of such a circuit being used?


texts: Can a 3 phase IGBT based front end converter work without line reactor?

texts: I have been working on developing a 3 phase active power filter, which has a 3 phase IGBT bidirectional converter. I have been able to develop APFC (Active Power Filter Converter) with the line reactor. However, when I remove the line reactor, and run the converter under open loop and only as a PWM rectifier, my incoming ac current shoots up which forces me to force trip my ac supply. Can anybody tell me if it is possible to run the converter without the line reactor?


texts:
There is a proposed design that could have a polyfuse tripping many times.  Is there any lifetime to these things?  Number of resets?  I looked here but could find no such spec.

http://www.littelfuse.com/products/resettable-ptcs.aspx

I'm a little worried by the design.. but perhaps needlessly.
I'll send littlefuse an email and ask there too.

Thanks,

I got a nice Qualification Report back from Littelfuse.  (nice fast response, +1 for littelfuse.)

It's not clear if I can share this document on line.. I've asked for permission.  There is a nice graph showing a linear increase in the fuse resistance with the number of trips.  About a doubling of resistance after 200 events.  (mean resistance went from 0.1 ohms to 0.25 ohms after 300 trips)  I assume that the trip current will decrease as the resistance increases... but there is no data showing that.

And here's something else.  The resistance increases if the device is left in the trip state.  This does not look linear, but again resistance increased from 0.1 ohm to 0.25 ohm if left tripped for 24 hours.

My conclusion:  These devices should not be used as repeatable current limiters.  But only as fault detectors.


texts: Using many resistors to scale down AC voltage

texts:
I've heard it's common practice to use many resistors in series within a voltage divider to scale down an AC voltage for both power dissipation and capacitance considerations (using 10, 100MOhm resistors in series instead of one 1GOhm in a voltage divider.)
Is there any type of formula/reference document out there that states how many smaller resistors is enough? For example:
Situation 1: I want a 1kV peak voltage-measuring circuit to scale down to 2.5V using a 1GOhm resistor. My thoughts were to use 10 100Mohm resistors, but am not sure if this is overkill.
Situation 2: I want to measure up to 347VAC using a 100MOhm resistor. Should I use 10 10Mohm resistors, or again is this too much?
I realize this will depend on the power rating and parasitic capacitance values of the resistors I choose, but also feel there must be some tribal knowledge answer to this as well.


texts: IMU Roll Angle - Correct when Stopped, Wrong when Moving

texts:
I have been using an MPU6050 (3 axis gyro, 3 axis accel, built in motion filter called DMP) on a car axle to measure axle angle when driving. On a long banked corner (2 degrees) the sensor reads 0 degrees while moving (~40km/hr), but when stopped it reads correctly (2 degrees). The physical axle angle is the same though in both scenarios.

I believe the lateral force from going through the corner is affecting the sensors interpretation of which way gravity is, and is adjusting the roll angles accordingly. See image;

Can anyone comment on how this might be solved?

For example;

Using a sensor with a magnetometer?
Using a sensor with a different filter?
Is this solveable at all or just an inherent factor of MEMS
sensors?

Time is a critical factor at the moment in my project.

Thanks in advance for your input

Edit 1: I've come across this thread where the OP seemed to have the same issue with MPU6050 and went to the BNO055 with some luck but had calibration issues. Then said the problem was solved with MPU9250 and RTIMULib (open source filter) in the last post. I wonder if adding in a magnetometer helped as it gives a fixed 3D reference point which is not affected by acceleration forces. Or perhaps he tweaked the algorithms in RTIMULib to get his desired output. I have yet to delve into the motion-fusion/filter algorithms. To date I have just been letting the MPU6050 do that internally in the DMP.
Any thoughts on these potential solutions?


texts: Is it possible for an HDMI cable to be "worn in"?

texts:
I have an HDMI cable running thirty feet between my computer and a TV. I've had various problems with the screen flashing, stuttering, etcetera, due to the signal not being strong enough to carry a 4K HDR signal over that length. However with two separate cables now, after experiencing those issues initially, they've just gone away over time: initially the screen would go dark every ten to fifteen seconds, then less frequently, and now it doesn't seem to happen at all.

This is challenging my conception of how cables work in general. So, my question is... can a cable be "worn in" by use and carry a signal better over time? Or is there another likely explanation for this behavior?


texts: CORTEX-M LPCOPEN USB-VCOM basics - proper way to build a simple FSM

texts:
I'm working on a project involving the LPC4370 mcu (LPC link 2 eval board) and Matlab. I need my embedded code to be user-reconfigurable from matlab: the user sends a command, the mcu replies.

I'm using LPCOpen VCOM example as base: it uses USB w/ interrupt.

My C code:

static uint8_t g_rxBuff[256];
[...]
while (1)
{
        /* Sleep until next IRQ happens */
        __WFI();

        /* Read cmd */
        rdCnt = vcom_bread(&g_rxBuff, 1);
        state = g_rxBuff[0];

        if(rdCnt == 1)
        {
            switch (state)
            {
                case 'a':
                    /* cmd ackn */
                    vcom_write((uint8_t*)&g_rxBuff, 1);

                case 'b':
                    /* cmd ackn */
                    vcom_write((uint8_t*)&g_rxBuff, 1);

                case 'c':
                    /* cmd ackn */
                    vcom_write((uint8_t*)&g_rxBuff, 1);
            }
        }
}

Here I wait for a command and then I try to echo it back to host (i.e. ackn).

In Matlab

BaudRate=115200;
serial_object=0;
delete(instrfind('Type','serial'));
serialInfo = instrhwinfo('serial');
serial_object=serial('/dev  /ttyACM1','BaudRate',BaudRate,'InputBufferSize',4*4096,'OutputBufferSize',4*4096);
fopen(serial_object);

sendCmd(serial_object,'a');
sendCmd(serial_object,'b');
sendCmd(serial_object,'c');

Where

function ret = sendCmd(serial_object, cmd_sent)
  fwrite(serial_object, cmd_sent, 'char');
  cmd_read = fread(serial_object, 1, 'char');
  if (~isempty(cmd_read) && (cmd_read == cmd_sent))
    disp(strcat('SENT:  ', cmd_sent));
  else
    disp(strcat('ERROR:  ', cmd_sent));
  end
end

So this basically never works.
I always get errors like:

  Warning: The specified amount of data was not returned within the Timeout period.'serial' unable to read any data. For more information on possible reasons, see Serial Read Warnings.

Since I've been working on this for a while now I can tell that port set-up is ok, I managed to get data out of the mcu with the same configuration.

So I think I'm missing some how-to-basics here. The only assumption I made is that the USB IRQ is triggered everytime Matlab writes to the mcu.

EDIT: Some more infos from the debugger.
Here's IRQ calls after 1 matlab fwrite:


texts: Can someone explain to me what the 1s catching problem is in the Master Slave Flip Flop?

texts: I have read the explanation in my textbook but I feel that they are too complex and no matter how much I try to understand it I don't seem to get what the difference is when the 1s complement occurs. I have attached a picture where I got out of the book and I circled the part that it refers to as the 1s catching problem, but I don't see anything wrong with it.. It looks normal to me.. Can someone show me what it is "supposed" to do at the 1s catching area? I just don't see anything wrong with it....


texts:
We have the BJT transistor in the figure.

I have to do the DC analysis of the circuit, then draw the common base transistor scheme  of the circuit. I know the values of \$V_{cc}\$, \$V_{be}\$, \$R_c\$, \$R_e\$ and \$β\$.

So I apply KVL just like I have pointed it in the figure.

$$I_BR_B=V_{BE}+I_ER_E-V_{EE}$$

then we have

$$V_{EE}-V_{BE}=I_ER_E+I_BR_B$$

then

$$V_{EE}-V_{BE}=I_ER_E+\frac{I_E}{β+1}R_B$$

Definitely we find that

$$I_E=\frac{V_{EE}-V_{BE}}{\dfrac{R_B}{β+1}+R_E}$$

Problem is, I don't have the value of \$V_{EE}\$. How do I do the DC analysis now?
Also can you please show me the scheme of the common base transistor in this case?


texts: Can I control a Microchip USB3300 Transceiver with a USB 1.1 host controller IP?

texts:
As the title says I want to connect to a USB 3300 transceiver (USB 2.0 revision) using a USB 1.1 host controller IP block.

Is this possible or do I need to conform to the USB 2.0 specification as the IP core I have located so far is the only one located so far the older USB rev. 1.1?

I am not looking for generic host functionality.  From what I understand I only need it to support a single peripheral device (a usb mouse) using OTG (On-The-Go) specification.

I am not concerned about speed but want to make sure this is compatible.

What information can help in determining this?  Any help is appreciated.

Host Core

https://opencores.org/projects/usbhostslave


texts: Metal Film Resistor: Coating Reliability

texts:
I am using this Power Metal Film Resistor - which as per the datasheet, is coated with a "red, non-flammable lacquer which provides electrical, mechanical and climatic
protection". Now, on my PCB, I have two vias to GND placed underneath the power resistor placed for thermal relief in case the resistor gets heated up. Maybe that was my mistake, but the interesting thing is, part goes in to the field and is returned because smoke starts emitting from the resistor. On debug, I realize that the lacquer coating of the resistor had been chipped a little exposing the metal body of the resistor. There was very little clearance b/w the resistor and the PCB and in this particular case, the resistor happened to touch the via - boom! short to GND and resistor began heating up.

Questions:

In this failing part, there might have been friction with another object or some mechanical stress that caused the coating to chip off, thereby exposing the potential problem (promixity to GND via). However, in other parts, assuming there is no friction - should I still expect the coating to come off, either due to normal ageing or due to moisture or thermal stress, etc?
It seems dangerous in general, if the coating of metal film resistors can come off due to mechanical stress - thereby exposing the metal body of the resistor to contact with say, the enclosure for example. Is this a known problem - how is this dealt with or prepared for?


texts:
I am attempting to make an LED light up using a capacitor.

My approach:
I am attempting to connect a switch, capacitor and LED in series. My assumption is that when i press the switch the capacitor will start charging. AFter i release the switch i expect the LED to light up for some brief amount of time.

Whats happening:
As soon as i click on th switch and LED lights up for an instance and goes off. However, (after holding the switch for approx 10-15 secs) i let it go, the LED doesn't light up.

Below is what the circuit looks like. Any feedback on my approach, circuit or on whats happening?

NOTE: The arduino board is just being used to power the circuit.


texts:
I was looking through previous posts and couldn't find anything that I was looking for on this topic. The waveform below is the input current to my system, which is also below. The question is, how do I go about getting the efficiency? Should I be taking the average or RMS value of this current waveform to get there?

Edit for question clarity: I was actually wondering if I should be using the RMS current for the input since this is not a pure sinusoidal waveform (the second half of the original post).


texts: How does writing a bit to a GPIO pin turn on my induction motor?

texts:
I have a Raspberry Pi 3 hooked up to a Yahboom 4wd robot controller board:
When I set GPIO PIN 2 to output mode, then write a 1 to it, the fan turns on. What actually happens, physically, that turns on the fan motor? I only know software/math, and basic physics, but never studied electrical engineering.


texts: Can thin sections of copper traces be used as fuses?

texts:
Is it safe to use thin sections of copper traces as one-shot fuses when cost is important, but when it is also vital to protect the rest of the circuitry? Should the solder mask be removed at that location? What about using 0R resistances in small packages as resettable fuses?

That's for applications when time to fuse is not critical compared to the location of the failure. For more demanding applications, are there I-t graphs of tracks of various widths available? I have not found any.


texts: Could someone help me identify this component?

texts: Short question here: could someone help me identify this component?


texts: How do I find an E.E. to partner with for a product?

texts:
I am a software developer and need to work with a partner who will design and develop a device (SIMPLE device) to interface with the iPhone hardware port.  I am not sure of the best place to find such a person.

This would be a part-time thing - it won't take much to develop it.

I already have the Apple hardware spec (through the Apple program) and now just need someone willing to design this.


texts: near field power density formula for a dipole antenna

texts: I am looking for a formula for near field power density from a dipole antenna antenna. Is  cylindrical model is sufficient? Do I have to consider ground reflection too? Please share your ideas?