texts: LM2776 Inverter is not producing -3.3v with 3.3v input

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Background

I am using a TI LM2776 Switched Capacitor Inverter (datasheet here) to obtain a -3.3v bias voltage for an LCD (Newhaven Display, NHD-12864MZ-FSW-GBW-L, datasheet here).

The LM2776 is connected exactly as shown in this digram from its datasheet:

Vin is 3.3v, EN is connected to Vin, and I'm using the same capacitor values.

Question

When I turn on the circuit with no load, the output of the LM2776 is about -0.9v. When I connect it to the LCD bias pin to load it, the output is about -0.7v. Why am I not seeing about -3.3v?

Other Notes

LCD Load

When I connect the LCD bias voltage pin to a DC power supply (at -3.3v) instead of the LM2776, the LCD draws about 20mA, so the LCD should be an appropriate load for the LM2776. According to the datasheet, I shouldn't be seeing any significant voltage drop at this current draw:

Capacitors

All capacitors are ceramic X7R radial capacitors.

Layout

The circuit is currently on a breadboard, and the LM2776 is connected to it through a SOT23-6 -> DIP adapter. I know these devices can be sensitive to layout considerations, but the same configuration worked a couple of weeks ago, and I have no reason to suspect there was damage of any kind done to it since then.


texts: Using an Arduino to read data from serial device then send data over bluetooth

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So from a general high level standpoint I need to grab data from a serial device and then send this data over bluetooth. I have a bluetooth modem picked out. I understand how to hook it up to the arduino. I however do no know how to hook the a serial device that will talk to the arduino.

It seems like I am trying to do too many simultaneousness serial connections.


texts: How calibrate an RGB LED to get correct color mixing

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We are using RGB LEDs in our product and we require to emit white light to indicate a certain state. But because of the tolerance of the resistors and the LED itself it is hard to achieve the same white color in all the devices(some are reddish white, some are yellowish). We are driving the RGB leds using PWM with 255 duty cycle.

In order to solve this we decided to use a color sensor to calibrate each RGB led on the product using a color sensor(We are using http://wiki.seeed.cc/Grove-I2C_Color_Sensor/) . What we would like to do is to store a calibration value that corrects R, G and B (e.g. by some multiplication factor) so that mixing of colors can be achieved accurately for not just white but any color. But unfortunately color sensor channels(RGB) data and its correlation to PWM value is not straight forward from what we understand. Could anybody help us out with a solution.

Thanks in Advance,
Prasad


texts: DC 5 Volts - 2100mAh Electric Motor Generator. How?

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I have spent my entire weekend trying to locate a place where I can buy a 5 Volts - 2100mAh Electric Motor/Generator. My goal is to spin this motor up to a certain RPM to generate the 5 volts and 2100mAh required to charge an iPad. It's an experiment I've been trying to accomplish for some time now.

Can you kindly point me in the right direction? Is there such a motor in the first place? If I need to somehow modify an exiting one, where can I read about doing so to these specifications?


texts: Can i use MOSI/MISO pins from this schematic

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Can i use MOSI/MISO pins from ATMEGA328 to use for ICSP programmers. I am already using clk and data as inputs to control my 7-segments. I want to use the icsp but i already used the miso/mosi pins for my 7 segment already, does it make sense to have a uC pin be used as outputs for both the 7-segment and the ICSP header.

Thanks.

Edit: Sorry for the confusion all i have updated  my question.


texts: Best practice design ground and shielding

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Case:
I design a pcb with a microprocessor and a adc (I'll leave out the details).

Is this correct:
The digital ground and the analog ground should be connected, but by a small passage.

Next question:
If the pcb have hole's for mounting to a metal chassis, should the skrew's then be grounded to the pcb analog/digital ground and to the chassis? Wouldn't that be a better protection?

Or should the analog and digital ground not be connected to the chassis. Instead I should design a "chassis ground" surrounding the digital/analog ground.

Or should the analog/digital just be on the pcb and not connected to the chassis nor should the be any chassis ground either.

Kind Regards


texts: How to do PWM with least ripple in software?

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I'm interested in generating a PWM signal in software on a micro (it is not possible to use hardware PWM in this case).  It is simple to use (for example) a loop with a counter that counts to 255 and wraps around, and transitions high-low when the counter hits N and low-high when it wraps around, for an N out of 255 pulse.

However, because this PWM is rather slow, I would like to smooth it out, as follows: if the output is (for example) high for 2 out of 255 counts, I would like the output to be high during the the 0th and 127th count, not the 0th and 1st.  If it is 127 out of 255, I would like to transition low-high and high-low every count, instead of staying high for the first 127 and low for the last 128.

In other words, the lows and highs should be as evenly spread out as possible.  I realize when the PWM is near either extreme of the range it would still have a large ripple, but this will reduce ripple a lot near the middle of the range.  How to do this in an efficient way?

EDIT: It seems like I have rediscovered Pulse Density Modulation.  I'm still not sure how to do this in practice, especially in a fast loop.


texts: Is it safe to change battery replacement for equivalent with similar voltage?

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The battery of my old drill is dead. It is not charging anymore. It contains 10 batteries NiCd 1.2V, 2A serially connected. I found the correct replacement but those are expensive. I am planning to replace the batteries using 4 18650 Li-Ion batteries of 3.7V 2.2A each (serially connected as well). I understand the voltage will be not the same but it is into the drill input voltage range.
My concern is more about the impedance of the 10 serial batteries VS the 4 li-ion batteries. The resistance of the 10 batteries for sure is bigger than the others. So the electric current delivered to the drill can be more that what it can handle.
What do you think, could my idea work or better buy the expensive but secure batteries?


texts: Make Boolean logic equations from circuit?

texts: I think I'm doing my Boolean algebra wrong on this circuit. Could someone check my work here?


texts: Can a server send data to my SIM800c while it is in sleep mode?

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I have a SIM800c and I'm also using an adafruit.io server. I'm building an alarm system and I'm wondering if I will be able to send commands to the system using the server while the GSM module is in sleep mode.The way the commands work is I update a feed on my server and my device detects that via the cellular network. It notices changes because it has "subscribed" to the feed.

My device uses the MQTT protocol to communicate with an adafruit.io server. When a device is subscribed to a feed, it takes note of any changes that occur there. A feed is basically just a list of data. When a value is added to the feed, any devices that are subscribed to the feed notice.

To give you some context, my alarm system has 2 commands, arm and disarm. I want to put the GSM module in sleep mode while its not being used in order to save power. I'm concerned that the device wont be able to respond to changes in the feed on my server.

I would test this myself and I will as soon as I can. I just don't have the PIC device yet, so I figured I would ask and see if the answer is out there.

I've included the datasheet for the SIM800c. See this following link: Elecrow Hardware Design PDF.

See the attached image. It says it can still respond to data calls while in sleep mode. I'm just not sure what that means. Does that mean that if my device is subscribed to a feed, and the feed changes, the device will still notice it? It's all done through data.

What do you think?


texts: RS-550 DC motor controller 24V (35-70) A working range and a stall of 120A

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I am currently designing a motor controller for a SUMO robotics challenge.

Each of a two motor setup exhibits a (0.15-0.40) N.m torque resulting them pulling (35-70) Amps nominally and a peak of 120 Amps when stalled (this happens frequently).

The driver needs to be compact and relevantly small. (12x9) cm is kind of the maximum.

I am having trouble finding a good technical guide to designing a proper power mosfet H-bridge controller for the motors. I know all the theory needed but I need a guide that deals with all high current related issues.

Here is the motor curve with working area highlighted in blue.


texts: A project I'm exploring requires placing a permanent magnet in close proximity to an RFID tag (within a cm or so). Can an RFID tag be read when there's a permanent EM field so close to it?


texts: Is it possible to use a DC-DC BUCK-BOOSTER instead of a Solar Charge Controller or M.P.P.T in solar Charging?

texts: DC-DC Buckbooster vs M.P.P.T vs Solar Charger


texts:
I produce a magnetic field with a current source and a long cylindrical coil. A current of \$\hat{x}\$ (peak value) with frequency \$f_{x}\$ produces a magnetic field of \$B\$ (RMS value in Tesla) with frequency \$f_{x}\$ that I can measure with a magnetic flux field sensor, e.g. a Hall-sensor, or a fluxgate  sensor. When I read the analogue signal with some A/D-card, I can plot the spectrum, which should give me a peak at frequency \$f_{x}\$ and amplitude \$B\$ with the unit Tesla plus some system noise. With some mathematics, I can calculate the spectral density of the spectrum which has the unit T/\$\sqrt{\text{Hz}}\$. Now my question:

Question: What is the physical interpretation of a sinusoidal signal per sqrtHz?

For noise one has to consider the ENBW so it makes sense. For a sinusoidal signal, noise and bandwidth do not fit in the context for me. For the transformation one of course needs to consider resolution bandwidth and window type which determines the ENBW used for the conversion. But does that have physical meaning? As a matter of fact, it is not possible to plot a RMS signal and noise over frequency at the same time, because they have different units.


texts: Question about AD834 + AD811 as voltage controlled amplifier

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According  to page 15 of AD811 datasheet , it can be used as a voltage controlled amplifier in conjunction with AD834 . In the schematic below, I am a bit confused about the configuration.

If we assume that W1 and W2 are in phase shift=π and supplied by AD834 internal Open collector transistors which are configured as common emitters by external resistors, it easy to understand that AD811 is working in a differential mode. VG stands for gain control voltage ( between 0-1v ?) and I think Vin must be the input signal. but what I can not understand is the + point in the schematic (red arrow in the schematic below).

What is this point connected to? it can not be V+ because 12v is well above the maximum ratings for inputs (page 4 of AD834 datasheet: with 11mA in Vs+ and R6+R4= 294+182Ω , we have 5.2v drop in VS pin but the maximum allowed Vin is equal to Vs). On the other hand AD834 is designed for working in +/-1.3 clipping voltage between X and Y and a positive voltage above 1v on this pin simply goes to its clipping region.

My questions are:

1- To where the indicated point is connected?

2- On page 15, line 10 of AD811 datasheet, it says that the gain is -70dB for VG=0 dB and 4 for VG=1 volt. I think this dB is a typographic error. If it is really dB and not volt, it may mean that for gain=-70dB we need to connect Vin to VG. Is it correct?

Any suggestion appreciated in advance.


texts:
Most digital circuits can be built in more than one way. However, the easiest way I've seen to build an edge-triggered D flip-flop is with a pair of D latches. One has WRITE connected to CLOCK, the other has WRITE connected to the inverse of CLOCK. This way, one latch is always write-enabled, and which one changes whenever the level of CLOCK changes.

simulate this circuit – Schematic created using CircuitLab

What I ended up doing is to have two separate clock inputs instead. This way I can ensure that they're never both high at the same time; I can put some dead time where both of them are low.

simulate this circuit

Is it common to do something like that? Have I reinvented a common technique that has a name? Or is this a totally off-the-wall crazy way to design circuits?


texts: What are the effects we need to consider when transmitting extra low voltage (0.1 uV) signal over ~1m long cable?

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What are the effects we need to consider when transmitting extra low voltage (0.1 uV) signal over about 1 meter of cable, either coaxial or shielded twisted pair ?

The source is low impedance (~5 ohm), and the receiver would be high impedance amplifier input.
The signal is about 10kHz in bandwidth, in the 10 kHz to 50 kHz range.

Cable impedance matching is not an issue at these frequencies, for transmission line effects the cable is probably too short.

I would guess that shielding efficiency would be a primary concern ? would triboelectric noise be significant in these conditions ? Anything else ?

EDIT:
The context for the question is working out the noise budget for a complete signal path (physical medium -> sensor -> preamp -> cable -> main amp -> ADC -> digital signal processing gain), to aid in exploring the trade-off of placing the cable after preamp vs after the ADC (in the digital domain).


texts: How is the differential mode noise suppressed by adding a capacitor across the Lines

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I was reading about the common mode noise and differential mode noise.

I don't understand how a differential mode noise gets coupled and how adding a capacitor across the line will help.

I understand about common mode noise. Like, if we have a noisy source, it might equally couple on both lines and we can use a common mode choke to reflect back the common mode noise back to the upstream source.

But how is a differential noise generated on the lines?
Is it generated by places the lines close to differential signals?

My questions:

In general, does the noise affect only power lines or signal lines as well? I am asking because, I have seen app notes and other illustration depicting these concepts only in the context of Power supplies.
Is differential mode noise, generated on the lines, by placing the differential mode signals near them? Or how else, will the line and neutral wires have noise voltage of opposite polarity? I assume that differential mode noise is obtained only by placing the circuit near differential mode signals. Am I correct in this understanding?
And I understand how a common mode choke attenuates the common mode signal. But how does adding a capacitor between the lines, attenuate the differential mode noise? Can someone provide some help on this.

Thank you


texts:
I am using diodes to bias tubes for the input stage of an audio circuit.  They will hold the cathode off ground by their forward voltage (Vf).  Current will probably fall between 1 and 2 mA, and the voltage will be set by the diode's Vf.  I am aiming for .8V-1.6V total, and I can have diodes in series to obtain the right bias voltage (thought multiple junctions tend to raise the noise level).  Peak-to-peak AC will be in the 250mV range.

I would like to know if anyone is aware of low noise, low distortion diodes that will have minimal effect on the audio signal passing through them.  I've experimented with several types, Schottkeys, 4007, 914, etc.  The Schottkey rectifier diodes and the 4007s are best so far.  Of course, at 1mA, their rated Vf is quite different from the specs that are usually published.  Only the most complete spec sheets show Vf below 10mA or so.  The Cree 6010s (rectifiers) came in at .8V and the 4007s came in at .5V.

I realize that most people don't use diodes in this application, so information has been hard to come by.

imagine a triode tube, the anode is fed 155V through a 75K plate resistor, the grid is fed from the output of a microphone capsule and has 200Megs to ground. The cathode has two 4007 diodes in series to ground. Signal is taken from the anode, through a capacitor to the an output transformer. This results in 1V of bias at at the cathode, 75V on the anode, and 1.5mA of current flowing through the tube. The diodes each provide .5V of the total bias voltage and are, themselves, biased by the 1.5mA of current. The diodes never see negative voltage


texts: Does MCU RAM size affect quality of WAV read from SD?

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I'm planning to build a cheap and compact WAV audio player that reads audio from a microSD card using Petit-FatFs. The Petit-FatFs driver is designed for use with devices with less than 512B RAM. My idea was to use an ATtiny X5 series MCU, but there are three variants:

ATtiny25 - 2kB flash, 128B SRAM
ATtiny45 - 4kB flash, 256B SRAM
ATtiny85 - 8kB flash, 512B SRAM

The firmware does not occupy more than 2kB.
But does the RAM size affect the audio quality? I don't want more RAM than necessary.


texts: ESP32 - Guru Meditation Error when External load is plugged in

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I would like to power following ultrasonic sensor using the ESP32:
https://www.maxbotix.com/documents/HRXL-MaxSonar-WRS_Datasheet.pdf
Using this Heltec ESP32 board:
https://heltec.org/project/wireless-stick-lite/
This board comes with an 3.3V switch denoted as Vext or Ve that is controlled by GPIO Pin 21.
Everything works quite nicely besides it throws me an error if I plug in an external sensor on the Vext pin:
https://www.maxbotix.com/documents/HRXL-MaxSonar-WRS_Datasheet.pdf
The external sensor is an ultrasonic sensor with a nominal current consumption of below 3mA.
Please see the error here:

For the Vext pin, the error always occurs but strangely the error even occurs if I unplug the device during operation and plug it into the 3.3V port of the board.
This question is probably entirely related to the hardware design of the specific board but eventually you have some ideas why this Guru Meditation error can happen. Eventually due to some voltage spikes that occur while plugging the sensor in or off?
I can probably find a stable solution if I just leave the setup alone but I haven't experienced that error related to power issues.
Thank you!


texts: Can I pedal power a laptop device while the device is being used?

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I want to research how easy it would be to use a small laptop device while powering it by pedaling on a stationary frame. (For example, using a tablet on an exercise bike, or using a netbook while pedaling at a desk.)

I already know that it is possible to run a laptop with pedal-power, because I have found several examples of this being done. [1] [2] I now want to construct such a setup for my academic study. I need to confirm exactly what I need before purchasing the equipment. I do not have a background in electrical engineering, so although I have lots of numbers I don't know what I need to calculate or consider to pick a feasible option.

POSSIBLE TARGET DEVICES:

netbook: adapter's input: 100-240V 1.7A, output: 19 V 65 W [3.4 A]
tablet: adapter's input: 100-240V 0.45A, output: 5.1 V 2.1 A [10.7 W]
smartphone: 3.7V 4.44WH (all the information I have)

POSSIBLE ARCHITECTURES: Apart from the seating arrangement (bicycle, recumbent bicycle, desk) there seem to be several options for how to hook the equipment up:

wheel > bicycle dynamo > regulator > device (powerful enough for the tablet or the netbook?)
pedals > DC generator > DC-DC converter > regulator > device
pedals > DC generator > charge controller > battery (e.g. lead acid) > inverter > device [3]

Additional data:

An adult can generate 50-150 W in the course of an hour's strenuous pedalling. I want my users to be pedalling comfortably rather than strenuously.
Any device will have its own battery, so could I eliminate the need to have a battery in the setup?
Is it a bad idea to hook the device up to the regulator directly in order to avoid using the device's own adapter?

QUESTION

I'm very confused about a way forward at this point (even if it seems like I'm not). What I am looking for most of all in answers is clarity and definitiveness.

Of these combinations of devices (1-3) and architectures (1-3), which will definitely work?

Which combinations should I strike from the list as they categorically will not?

The dynamo architecture looks good to me because it seems easier/cheaper to hook up - is it capable of powering all these devices, even the netbook?


texts: Increase runtime: batteries in parallel -> buck || batteries in series -> boost

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I have 18650 batteries, I created 4S packs with 6P in each.
I have a 12 V 2 A solar panel and I want to use this panel to charge them ( i know I need a charge controller and I must balance charge them )
My main question is:
I have two 5 V devices (Arduino and a power bank charger) that I want to power up with these batteries.
I have two 12 V LED strips each drawing ca 1 A.
Should I put all these 24 batteries in parallel to get my 5 V and use a boost for 12 V or use my current 4S6P and step down to 5 V?
Which setup will give me more runtime?
Having 24P will have an easier charging circuit.


texts: Is there another way to interface with BeagleBone Black hardware

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As an example, to turn on one of the on-board LED's you need to update the text file "/sys/class/leds/beaglebone:green:usr0"

In writing some tests just turning on and off lights, it's very slow. I believe this is because it uses the file system instead of directly interfacing with the hardware via an API or memory addressing.

Just wondering if there is any other way other than the file system. I don't know if this is a Linux thing or a BeagleBone Black thing.


texts: Brightness issues driving 10*11 SMD 5050 LEDs matrix

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I'm working on driving a 10*11 LEDs matrix by a µC since a while, and I decided to come to you because I'm a bit surprised/annoyed by my results.

So, I first started with simple 5mm white LEDs either 74HC595 or TPIC6B595 shift registers for driving rows and columns, as it seems to be a kind of "standard" method. The matrix was working pretty well, but the brightness was far less than expected … I know that I can't expect the same brightness than a continuous mode 5mm LED because of multiplexing. I noticed that on forums, people always advice to put transistors array as power interface between shift registers and LEDs, but as expected it doesn't change anything for me because my TPIC6B595 shift registers were able to sink enough current.

As my goal is to obtain the same brightness with my matrix than a continuous mode 5mm LED, I decided to try with more powerful LEDs and so I get SMD 5050 (PLCC6 3.1V 60mA) ones, using all of the three modules inside of them. I changed my shift registers for an HT1632C which is a dedicated component for LEDs matrix driving.

I followed instructions from HT1632C datasheet, especially the following diagram :

The results were more or less the same than the first ones (I succeeded in getting more brightness due to 5050 but not enough to reach continuous 5mm). So I decided to do several tests by connecting LEDs to 5V through resistors (to aim to get nominal current through them), and then without these resistors. I noticed a slight difference concerning the brightness but not so much.

I chose to come to you because It starts to drive me crazy. I may have missed something obvious ? Probably … !

I don't know what is the usual way of doing this, for example if LEDs can be overcharged without risks (because they are pulsed) or something else ?

In brief, what I'd like to get is a 10*11 SMD 5050 LEDs matrix which permits to get almost the same brightness as 5mm LEDs in continuous mode.

Thank you for taking a bit of you time to help me solve my problem.

Regards.


texts:
I need to design a "peak" power current supply circuit for my load. Power specifications of load are below;

Continuous power consumption: 12 V 5 Amperes DC.
Peak power consumption: 12 V 10 Amperes DC.
Duration of Peak power consumption is 1 miliseconds with a repetition           period of 2 seconds. Time chart is below;

Input voltage of will be designed circuit is 18V-36V DC.
I can put a DC to DC converter that can be supplied 12 V 10 Amper, however i dont want to use, I have to use 12 Volt 5 Amper DC to DC converter and an extra circuit when peak current can be seen. I need this circuit design.
I know in electronic, capacitor and inductor can store energy on their own. So can anyone help me to find or learn for this circuit?

Thanks,
Cem


texts: Why does the power strip's switch light turn on even when the switch is off when I plug in a Schuko plug (CEE 7/7)?

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I have a European power strip Schuko socket with switch (it looks like this

and this).

Mine has 3 Schuko sockets. I cannot open the power strip because it has round head carriage bolts with fastner-like threads(what's the name of their thread?) instead of screws.

Its Shucko plug (CEE 7/7 plug) is connected to a Shucko socket (CEE 7/3 socket) in the wall that has only one live wire (I've checked), which is the normal way things are here, and I'm pretty sure the ground is properly connected. Someone mentioned that's possible both wires can be live but this is not the case for me, that's why I mentioned this info.

The power strip and its light switch seem to work as intended, except when I connect my newly defunct washing machine (which stopped working during the last rinse cycle, for reasons yet to be determined).

The machine acts as if it's not receiving any power, however the power strip's light switch remains lit regardless of the power strip's switch's position (on or off) when (and only when) this washing machine's Schuko plug (CEE 7/7 plug) is connected to this power strip.

What and why could cause the power strip's light switch to light up even when the switch is in the off position ?

Connecting other plugs into the power strip do not cause the switch light to light up while in the off position! So there must be something that the defunct washing machine "does" internally that's causing this.

I've tried rotating the Schuko plug of the washing machine but the switch light still stays lit while in the off position.

However, I just tried rotating the Schuko plug of the power strip itself and it worked: the switch light is no longer lit while in the off position.
Frankly I don't remember if the light was ever on while the washing machine was previously working(as in, not defunct) and the power strip's switch was in the off position. I do however remember the power strip's switch light being off when it was turned off, while the washing machine wasn't defunct, without having changed the power strip's Schuko plug wall position! This leads me to believe that somehow the washing machine defunctness is the cause of the power strip's switch light being lit even while in the off position, but I've no idea why would this happen!

UPDATE:
I was able to take the following picture from inside the washing machine:

The white pipe-looking thing is the power cable.

EDIT: To get a clearer idea of how the above actually looks like, here are two pictures from somewhere else:

Apparently it's called a "Surge filter". So I can only infer that the way it broke makes the off position of the power strip switch's lamp light up.

UPDATE
I pulled out the surge filter from the washing machine, here's a better picture of the meltage:
(I can't upload images for some reason(imgur won't do anything), so here's the link)
https://user-images.githubusercontent.com/40925413/47820832-fdd41880-dd5e-11e8-8171-9fc270164ac6.jpg

I've also broken into the power strip (because it wasn't working too! took me a while to realize because I didn't try to use it until now). So one of the contacts inside the red switch was melted into the plastic, no doubt a side effect of the above:
https://user-images.githubusercontent.com/40925413/47820826-fa409180-dd5e-11e8-9eee-278c014d31d9.jpg


texts: Filters generate output even if they are not connected to any signal and does respond differently to different signal sources

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opAmps are fed by +/- 9V.

I have two more filters like this one, in total three filters.

If I use a signal generator as input signal and observe output via an oscilloscope; all those filters give me satisfying results(not the same with simulated results, but close enough considering I am using %5 resistors and other possible non-idealities.)

However, in reality, the input signal comes from a microphone output. And mic takes sound from a 10 cm away speaker(it is being so loud that, microphone gives around 600 mVpp directly(***), without any amplification done.) At this point, the problems start to occur.

(***) - is this normal? I mean I always saw that microphones give output in the range of maybe tens of milivolts while I was doing research on the web. The microphone is an electret one, and I don't have any datasheet or so.

The filters which works fine before, starts to behave problematic. For example, even if I don't connect any input signal(the output of mic), the filters output a sinusoidal-ish waveforms around 400-500 mVpp at their(filter's) designed center frequency when the loud speaker is on. I even connected input to ground, but did not help. One thing I could not understand is why filters interact with sound when there is no physical(electrical) connection with the microphone?

Also, when connected with microphone, the filters still does not behave as before. I think it might be resulting from some kind of loading effect. There is a clear difference between mic out and signal generator out, which I could not figure out. Two things I suspect are,

The filter opAmps are NE5532 which has a very low input impedance of 30k ohms or so.
I think adding a voltage buffer to microphone output may help since it will(?) make output impedance more similar to the output impedance of a signal generator, but I was not sure and did not try.

I am also attaching the mic driver circuit, which is pretty simple.

It is the exact circuit in my implementation with +9V instead of +5V.

The microphone output itself is fine, it gives pretty similar waveforms to loudspeaker output.

I might look combining two questions in one, but I could not be sure if they are related whith each other or not.


texts:
I need the input from you electro-wizards. I'm in the Philippines, the power is 220v, 60Hz. In most places there is an absence of a ground line.

Lots of people in our area have issues of getting "zapped & bitten" when touching metal parts of table lamps, etc., and even resting on the palmrest of my (aluminum cased) laptop I get the occasional "bite"

To me it is bizarre, but if I connect ONLY the + lead of the voltage tester to the live line I get a power reading , usually between 40 - 60 volts.

I am at  loss as to why I get a voltage reading when I connect only to the live line. If I test between the line and neutral I get the expect 230v.

We've ordered up a ground rod and will be driving this in next week to ground the neutral line and another one will be driven into the ground to act as a true electrical ground.

It isn't causing any great problems (yet), but I am trying to figure best how to resolve these issues.

Cheers,
Tim


texts: I am wwondering what a certain parts of the drawing mean. For example in the picture below, what mens 24x in front of the some dimensions? In the down-right corner, what are numbers 0.1 and 0.05 for and M within the circle?


texts: Is it possible to measure energy consumption from power socket?

texts:
I wanted to know if it is possible to measure how much energy is being consumed in the entire house by plugging in a power meter in any power outlet in the house?

I am aware of some portable meters but they can only measure energy consumed that specific appliances but not of entire house.

Sorry if the question sounds stupid, i am new here


texts: Quick-connect terminals - how to mount/connect them? Or Alternative PCB switches

texts:
I am currently designing a product for use in the automotive industry, and it will be used externally to the vehicle. I am at the awkward stage of trying to combine PCB design with product packaging/external/mechanical design considerations. External packaging will most likely be molded and reasonably thick (2-3mm at least) ABS plastic, with cut outs or recesses for human interaction mechanisms like buttons, switches, and/or some LED indicators.

The design is quite space limited, think about the size of an old VHS cassette tape but not quite a long (aiming for about 120mm x 120mm x 40mm external dimensions) and will end up being most likely a double-sided PCB with heavy population of components.

I have been looking at trying to use everything PCB mount, so that wire harnesses and assembly process during manufacture is a painless as possible. I feel bad for the Chinese factory workers..

Even though it's not directly a PCB mount device, I was thinking of using a SPST push button for on/off such as this one:

Cherry pushbutton

or a rocker switch on the side of the case like this one:
Rocker switch

But as you can see, it has these annoying "snap in" or "quick connect" terminals on them, making it both hard for me to mount this directly to a PCB, and even worse for right-angle mounting which is preferable.

Does anyone have recommendations/resources for how to design PCB footprints to accommodate these kind of "pins", or can recommend a cost-effect way to mount or connect these parts?

My easy alternative is a right angle PCB slide switch, but it may not be robust enough for the elements and possible heavy physical abuse from random "Consumers", who might buy automotive style products. I have looked at products like this:

through hole right angle slide switch

I am trying to avoid the really handy right angle through hole "toggle switch" components like this one: fancy toggle switch
because they seem a little expensive, and their metal lever is often too long and will be a nuisance. Help!

Also while i'm asking about manufacturing/product design, how can I incorporate surface mount LEDs properly when trying to make them visible to the outside world? Using plastic light tubes? Just little clear plastic windows?


texts:
I am currently trying to convert my ATX PSU to lab bench PSU. But I ran into a problem. I want to attach a dummy load, but I am not sure if I should use 12V or 5V.

On label it says that

+5V .. 21A
+5V sb .. 2A

+12V cpu .. 15A
+12V a .. 10A
+12v b .. 11A

Should I add those amperages together to see where is more power? Or how does it work when they are separated like that?

I am soldering all 12V together and 5V together too, so I think it adds up, but i am not sure, so I want to ask you.


texts: Resistor ratings for inductor fly-back suppression

texts:
I am building a circuit for user to interface with relays, and I am trying to build a protection to the circuit against fly-back from the inductor coil of the relay. Since there is no specific relay it is quite hard to choose the parts. All that is certain is the relay must be 5V and draws up to max of 250 mA (my recommended limit), but a protection for higher amp rating would be better.

The protection in my circuit is a diode - resistor combo. with the diode being 1n4007 which is greatly way more than what I need (which is good). the resistor is a bit tricky and what I am not sure about.

Assuming from what I know about inductors, is that it is a current source, and the voltage will depend on the resistor.

Here is my computation

V = I × R
5 = 0.25A (largest 5V coil current I found) × X ohms
X = 5/0.25
X = 20 ohms

20 ohms is for my absolute max, but for lower current loads it could go up to 50 ohms + (assuming 5V is our desired voltage). I don't know which is a better safe side value — is higher the better or the opposite? My guess is lower, but how low a resistor that generates 1 volt?

On a similar note, the power rating required for this resistor:

P = I × V
P = 0.25A × 5V
P = 1.25 watts

1.25 watt resistor are hard to find on resistor values that low. Will a 1/4 or
1/2 watt resistor work since the current is not continuous and it goes down?

Please help me if what I know is correct, thank you.


texts:
This is a simple battery powered toy basically just a DC motor.

Never use Ni-MH Batteries

Why would Tamiya 4WD JR prohibite rechargable Ni-MH batteries? As I understand it, the voltage is a bit lower, but beyond potentially lesser performance, I see no danger. Thoughts?


texts:
I am a software developer with little knowledge of Electrical Engineering. I have delivered some Raspberry PI projects that extensively use Relays.

I recently heard that Triacs are much cheaper and safer than Relays and can do the same job. If that is true, my question is:

Why are Triacs so under emphasised in Raspberry PI  (or Arduino) projects and people prefer using Relays?

Also, are Triacs suitable for 120V AC or is there any Triac that can control 12V DC as well?

Thank you,


texts: Battery powered vending machine. Possible or a pipe dream?

texts:
Is it possible to power a vending machine with some form of battery power for a 24 hour period!

Info I have on vending machines:

Most run on 115 V at 10.5 A.
Power usage is estimated at 3.1 - 4.4 kWh/day for lighting and 3.5 - 4 kWh/day for refrigeration.


texts: Why do I have to use an additional resistor with a photoresistor?

texts: I'm totally new to electronics and I wonder why we need to put a resistor in series with a photoresistor to measure the variation of light? I mean, photoresistor is already a resistor, why do we have to decrease the voltage in the circuit with an additional resistor? Thanks in advance for your answers.


texts:
I'm designing a home automation module and finding a way to supply power.

Is it possible to harvest energy from existing AC wire using step-up current transformer?

Also I can only find step-down current transformer for current sensing, where can I get step-up transformer? (Or it's not feasible?)

simulate this circuit – Schematic created using CircuitLab


texts:
I'm using a differential ACD from Microchip called MCP3424 and an ATMega16 to make various measurements.

Here is the schematic:

http://picul.de/view/HoR

Note: I have changed the values of R22 and R23 to 1.5k. MOSFET Q7 is off.

Today the ADC suddenly has stopped working. The ADC still responds to my commands but does a very weird thing:
Each time I write the config I actually read it back to compare it with an expected value to check for errors.
The weird thing now is that the channel selection bits (C1 and C0) seem to be stuck low. No matter which combination I choose these bits just stay low but the other configuration bits are still perfectly working!
I can't take measurements from the ADC either because the RDY bit always stay high (which means no new result).

I have the suspicion that the negative terminals (CH1- and CH2-) need to be connected to GND to ensure that the voltages on CH1-/CH2- never exceed the maximum value of Vss-0.4 however there are clamping diodes inside the ADC so I'm not entirely sure if that really caused the fault.

Notes:

I have taken ESD precautions, so damage through ESD is very unlikely.
The I2C part on the ATMega16 works just fine. I have checked the signals with an oscilloscope.


texts:
I wonder why is there no standard for Lithium ion batteries especially for portable devices,we can easily have a standard dimension/fit for similar capacities and power rating imposed by IEEE or similar organisations.
In this way we can use the ones of older mobile phones which do not comply to current protocols of 4g/5g
in other equipments like music players..
If we have standards for USB ports/bluetooth/wifi technology we can have for this too!
On top of that devices dont have a simple cover to dismount the battery nowadays!


texts: what is parallel run length in DRC check

texts:
What exactly is parallel run length in DRC check. I understand that there should be a minimum spacing between two metals depeding upon their parallel run length.

In the above figure R1 is the parallel length between polygon A and B. Should I also consider R2 between horizontal edges of ploygon 'B' as a parallel length with in the polygon ?

Please explain!


texts: Current loop receiver (minimal implementation)

texts:
I'm looking for a minimal design of a current loop receiver with the following characteristics:

I_in 0-20mA
U_in (-24) 0 - 24V.
U_out 0 - 3.3V

The precision doesn't need to be very high - an output voltage with a precision of +-5% proportional to the input current may be sufficient.
I was therefore looking first for a solution from a manufacturer and several forums. Unfortunately, I was not very satisfied with the solutions I found.
Either the presented solution was fully integrated within an IC and very expensive or it was too simple or too expensive, in terms of functionality:
1) Simple Shunt
The most frequently found solution was a simple shunt resistor with the high-side connected to an ADC or connected to a buffer and then to an ADC.
This solution is for me too error-prone in terms of failed connection or overvoltage.
2) Fully Integrated IC
This solution may be promising, but I'm looking for a more general solution. Maybe even cheaper.
I thought about an AC-input optocoupler, with the following benefits:

I don't have to share a common ground.
Isolated input.
Connection order doesn't matter.

Possible Problems with this solution:

Current-transfer-ratio seems to be in a wide range with low-cost optocouplers.
Current-transfer-ratio may be asymmetric.

Can someone recommend a possible solution or add some thoughts about my idea?
EDIT #1
After the first answers and comments I came up with this conclusion:

I draw this picture, representing the mentioned states.

Normal operation.
Overvoltage, the voltage gets internally clamped and the protection resistor drops most of the overvoltage.
Pin swapped, the voltage gets internally clamped and the protection resistor drops most of the reverse voltage.

As I understand a TSV diode in parallel with the resistor would now only protect against fast voltage change if the internal circuit is not fast enough to react.
Therefore my next point is, what if the connection to the low side of the shunt resistor has a higher potential than the ground potential on my board. Wouldnt that lead to a ground loop carrying some current?


texts:
I wondering if this is a safe and working schematic.
At AC voltage equal to or larger than 40 volts then switch goes to normally open and the battery (common) connects to load 2. At AC voltage source less than 40 volts the switch remains on normally closed and the battery is connected to load 1.

Given that there is an AC source and a battery source in this circuit but they don't interact this circuit is still safe?


texts:
1 GigaOhm resistors are so damn expensive.

(Don't ask, I'm trying to build a large diaphragm condenser microphone from scratch)

As an microphone pre-amplifier I am trying to bias a transistor and charge the capacitor plate at the same time similar to the setup in the Alice microphone circuit:

While I could just use AC coupling in between the capsule and the transistor base, I want to try and minimize middle-man components but also achieve decent amplification with little noise. I was wondering if it was sane to substitute the single 1G resistor with a current divider setup.

P.S: If the answer is no, I will have to resort to using a Popsicle stick instead.


texts:
Here's a circuit:

As you see there's a dependant source, 0.01Vx, depending on Vx, the voltage at the resistor of 150 ohm.

I don't exactly know how to handle this circuit properly. The presence of the dependant voltage source bugs me. I wan't to find Ia. Vs and Vab are undefined - I want only to expressions in terms of relations to Vs and Vab. I also want to know how to apply nodal analysis correctly.

I don't get how to apply properly KCL at the node 2.

First, I apply nodal analysis. I define node 3 as the 0 voltage node (ground).
Voltage at node 1 is Vx.

I end up with these equations:

\begin{equation}
\left[ \frac{1}{25} + \frac{1}{150} + \frac{1}{50} \right] \cdot Vx = \frac{Vs}{25} - \frac{0.01Vx}{50} + \frac{Vab}{50}
\end{equation}

First, is that correct?

Second, applying KCL bugs me. As said, the dependant source confuses me.
I basically must find the current between node1 and node2 and apply KCL. But... The dependant voltage source... does it add another current?
I would maybe try:
\begin{equation}
I_{a} = -\frac{0.01\cdot Vx}{50} + \frac{Vab}{50}
\end{equation}

But I'm not sure if Vab must be accounted in the KCL or not. I get headaches thinking about it.

Could you help?

Thank you!


texts: Can you create a 'Smart PDF' using Eagle?

texts:
I know on Altium that it is possible to generate a Smart PDF which generates a sort of bookmark for each component designator on a PCB layout, but unfortunately I have done my board design using Eagle 6.91.2 Lite Version and I not sure if it is a) possible or b) how to do it if it were possible.

I have the ability to print the design to a PDF but that doesn't work and even using the text recognition option on Adobe PDF Viewer doesn't prevail any useful results.

Apologies if this is not the correct place to be asking such a question as it is about a piece of software. However as it is a schematic editor I thought it somewhat suitable.


texts: What happens if I exceed the load my PSU is designed to deliver?

texts:
I want to use an old PSU I have for studying electrical engineering; to power my circuits. What will happen if I place a 0.6Ω load on the 12V output of a PSU rated for 10A?

I'm sure the PSU will heat up, but will it deliver its max current or will it blow up?

I could experiment, of course, but I don't want to risk ruining the PSU.


texts: 1V to 5V transistor amplifier for arduino digital inputs

texts:
I'm trying to use a soundcard to send a trigger signal to an Arduino. However, the software I'm using limits the output of the soundcard to between -1 and 1V, which is insufficient to trigger the digital pin on the Arduino.

Basically, I want to try and amplify this 1V signal to a 3.3-5V signal in the simplest way possible, maybe by using a transistor to route the Arduinos 5V supply to the digital pin.

This is somewhat time sensitive, and the only components I have available at the moment are some NPN transistors (2N2222) and a broad selection of resistors. Can I build a transistor amplifier to get the 5V I need? I'm new to this, so I am also not sure how/where to put resistors in this circuit. Any help would be greatly appreciated!

edit: Just to clarify, I'm using the soundcard to present a sound on one channel, and this trigger signal, in the form of a short pulse, to accurately estimate the onset of the sound from the arduino/for other experimental synchronization purposes


texts: Is there a way to solve this circuit using superposition or KVL?

texts:
simulate this circuit – Schematic created using CircuitLab

Using KVL :
\$-1 + 100(I_a+I_b) = 0\$
\$-1 + 100(I_a+I_b) = 0\$
In both loops I get the same equation, so I cannot know how much current is drawn from each individual battery w/o using symmetry.

Using superposition:
Shorting either \$Va\$ or \$Vb\$ is a problem mathematically, so cannot proceed further.

I'm familiar with KVL, KCL and superposition so far, I can guess from symmetry \$Ia=Ib\$, but this is somehow not satisfying me. Is there a way to find the individual currents through the batteries mathematically w/o using symmetry ?


texts: What does "zo <=500Ω" on the pin diagram means?

texts: There is device (viewfinder). It has "Tally" LED. On the camera's output diagram, on the "Tally OUT Indicator" pin there is marking "zo <=500Ω". What does it mean? Should I supply + voltage on this pin with 500Ω resistor?


texts: Charge a supercapacitor in 4-20 ma circuit

texts:
I want to design a charger circuit in my project.

At first I have a ic(AD694) for preduce 4-20 ma current,then must charge one 100F,2.7V supercap.

How can do it?

I want use a breadboard for this circuit.

I know some ic's such LTC3326 and sum LTM can use
But I want ic's can use on breadboard.

Maybe some one can offer other way.


texts:
I’ve got a power problem with a 16 x 16 matrix of addressable RGB LEDs.

OP's note: this 4 x 4 array follows the same pattern as the 16 x 16 version in the photo.

First, an R3 Arduino Uno supplies the value of each LED.
The LEDs are 5mm PL9823 (datasheet), run at 5V, and appear to draw 47.5mA at full white.

(Editor's note: notice that these aren't regular LEDs, they come with a controller that limits current and include a shift register in it - that knowledge will make the rest of question much easier to understand for some).

The Data Out of each LED is connected to the Data In of the next, thereby joining all 256 LEDs in series.
The first Data In connects to a 150ohm resistor, then pin 6 on the Arduino. This is a PWM pin.

None of the other LEDs have resistors, but I've seen a similar array done without them. This is because the resistors recommended by the manufacturer prevent the LEDs getting enough voltage for colour mixing, allowing only full red, green or blue.

They do, however, have a 100 nF capacitor each. This is a decoupling capacitor, with one lead attached to each power lead of the LED, thereby bridging the positive and negative terminals to supply more steady power as the light values change. The capacitors are mounted on the reverse side of the array.
The VDD and GND leads of each LED are joined in parallel, in two separate grids.
And of course, GND is tied back to the Arduino. USB powers the Arduino for now.

If my maths is right, the combined current of 256 LEDs on full white at the same time should be 12.8A. I have a regulated PSU rated at 30V @ 3A.
But the thing is, the current code for the Arduino is to drive only one light at a time, as a test. But the LEDs show no response when I switch the array on.
I have the current turned up to maximum. I'm drawing 3A but no voltage.

With my multimeter, I was reading 200mV on some LEDs, sometimes, and 0mV at other points. I don't know what the difference could possibly be, the setup is pretty evenly balanced.

I removed one LED to test and it still works fine.
In the beginning, I tested this whole arrangement but with a 9 x 5 array. Again, it worked fine. In this test I was drawing 1A even though the maths should dictate:
(9 * 5) * 0.0475  =  2.14A?

Could the power needs still be way too high for the power supply? My permanent solution was ultimately to locate a 5V @ 12.5A power supply, but I’d really like to be able to test my handiwork, to make sure it isn’t fried. Also I don't know if a 15A supply would be better, just in case, but I don't expect to ever have them all on, full white, at any point.

The goal is to be able to control each LED individually or in groups, using graphics libraries for Arduinos that generate geometric shapes and colour noise.


texts:
I have a standard sm-s2309s servo that comes with the Arduino starter kit. I have used it previously, multiple times without issue. Now I'm trying it to use my servo again but am unable to get the servo working. It simply does not respond. The problem could be either in the Arduino or in the servo itself.

I've tried various examples, like the examples from the Arduino book of the starter kit, or the examples of the Servo library reference documentation.

Servo myservo;
myservo.attach(9 /* or 10 */);
while(true){
    myservo.write(10);
    delay(1000);
    myservo.write(160);
}

Next, I used a multimeter to measure the voltage of the PWM port I use for the servo. The voltage changed depending whether a command for a 10 degree or 160 degree turn was issued - which means that the PWM ports - I tried multiple - are functioning properly.

Basic set-up for testing:

How can I test the servo itself, and perhaps find the issue?

I've opened it up:

Measured the wires to test for broken wires
It doesn't smell burned.
The little "motor" inside has a resistance of 41KOhm


texts:
I need to control a NSF/ODE JM R1 2/2 valve. Here the datasheet (Gofile link).
I cannot understand the electrical requirements. It says:

Power: 5W DC
Running power: 10 VA AC
Startup power: 15 VA AC

But I don't find anything about the minimum/maximum/nominal voltages. And I don't understand why there are specifications for AC and DC, and for DC there is no difference about running/startup power.


texts: Connecting multiple batteries to a battery tender / trickle charger

texts:
I have multiple 12V batteries, some small ATV starter batteries (12Ah and 9Ah) and some deep cycle (120Ah and 97Ah).

Can I connect all those batteries to the same battery tender in parallel?
Could I get only two chargers one for the small batteries and one for the large one?

At the moment the age of the batteries aren't the same. Some battery at full charge are around 13.4 and some 12.9.


texts: There is this voltage source that generates different types, it is not a sine wave properly (A), then passing it to a full bridge rectifier, the outcome is like B, then you use a smoothing capacitor and the outcome is like C, what do you use to generate a steady voltage? I tried with a 5V voltage regulator, but it is not working, and the inputs are usually higher than 5V. It is to charge a battery (3.7 V), do you strictly require constant DC?


texts: Best way to test a USB wall charger for output current

texts:
USB chargers are tricky. Or at least they are when you don't follow the standards.

I have a device that uses 5V to charge a battery. The device has a USB socket, with the idea of connecting it to any USB power supply (maybe USB power supply is not the best way to call them, but I mean a 5V DC wall wart that has a USB port, whether that wall wart adheres to USB specs or not regarding power delivery, I don't care as long it outputs 5V), but doesn't do any handshaking to ask for power. I was wondering what will happen if you use a charger from brand X or Z, will it output 100mA? will it output 500mA? will it provide as much as it is rated (e.g. 2A on an iPad charger)?

My question is, given that different manufacturers seem to use different ways to get more than 500mA from their chargers (at least to my knowledge) how can I get the maximum current a power supply can provide without needing to negotiate the power delivery? I was thinking in using an active load, but I don't know if that's the best way to test it. Is there any considerations I need to keep in mind to do the test?

I would need to get the active load, as I don't have any at the moment to test it myself and I wanted to ask first before purchasing it.

EDIT: The question seems to be too open to interpretations, but I don't know how to word it while keeping it short, sorry. I guess my question is: when using a charger that provides more than the usual 500mA, and that uses a proprietary system to allow the drawing of more current (e.g. a tablet charger from a reputed brand), what should my load by in order to extract the maximum current from it, without having to use ICs to do any kind of negotiation? Can I just connect a variable resistor and check when it starts to drop voltage? Can I get 2A from tablet charger that is obviously capable of doing it, without requiring whatever resistors it needs in its data lines?

I appreciate the answers given so far, as they are useful, but not exactly what my (terribly worded) question was looking after. I don't want to know how to measure that current, I know I can use one of the many flavours of ampmeter available, and I don't want to know how to do the negotiation to get more power. I want to know how to set up my test so if I get X amps, that's the maximum I can get from the charger without trickery.


texts: If we have generic memory component that is \$2^{16}\times8 = 524288\$ Bits wide and CPU that that has address bus that is \$17\$ Bits wide. How could I locate this memory to begin from address \$ 10000 \$ (hexadecimal "Hex") and what is the corresponding end address? Could somebody provide hints or tips?


texts:
I'm designing a product that will be fed directly from 220V mains. The 220V goes into a PCB that has a high voltage section and a AC/DC converter module to generate low voltage to the microelectronics.

When using 110V I always use a input fuse for overcurrent protection in one of the mains wire (Live or Neutral - whatever...).

For 220V, since I have two 110V phases, should I use one fuse or two fuses (one in each phase)?

I think that using a single fuse should be suffice. However if one of the fuses blows and the other stays intact the board still have a hot main wire attached. Even if no current flows because the other phase is out, there's still possibility of electrical shock or worse... am I thinking right?


texts: Recommended discharge current of coin cell

texts:
I am thinking of using small coin cells to power white LEDs (20mA @ 3V FWD voltage). When I look at some coin cell specs sheets, I've seen "recommended discharge current" of only a few mA or less (e.g. >1mA or >3mA). If I choose a cell with 1mA recommended discharge current, does that mean I need 20 of them connected in parallel to provide 20mA (assuming cell has 3V rating)? But I have seen cheap LED lights powered by a single coin cell rated at only 1.4-1.6V (perhaps the LED has much lower forward voltage, but current must be much larger than a few mA).
So what exactly does the "recommended discharge current" mean in the coin cell specs, or does it matter at all for simple electronic project like lighting up LEDs?


texts: I am charging an old (probably 90s or older) security system battery with 4 3.3v solar cells compounded and partly covered up to reduce the voltage. the standby charging voltage is 13.5-13.8v, and the solar cells are putting out 13.65v. first, is this safe? second, can I determine the battery life by the voltage outputted by the battery after a certain time of charging? third, is it dangerous to charge the battery with less than 13.5v?


texts: Can anyone provide an intuitive explanation for the filtering action of RC or LC circuits? I know the mathematical treatment involving reactances but I was wondering if that could be explained physically?


texts: Can I use 18AWG wire instead of 22AWG when doing guitar pedal modifications?

texts: I'm planning on doing some modifications to my Dunlop GCB95 Cry Baby wah pedal. As far as I can tell, the hookup wire in the pedal is 22AWG (it's difficult to read what's printed on the side). The smallest gauge of hookup wire my local hardware store had was 18AWG, and I decided to buy lengths of 3ft. in a few different colors. My thought process was that I should be able to use any hookup wire that is 22AWG or bigger. However, before I do anything to the pedal, I want to be sure that I won't run into any issues. Would it be okay to use the 18AWG wire, or do I need to get 22AWG wire?


texts: Output reflection coefficient of a two port network

texts:
In the third edition of the textbook Microwave Engineering by David Pozar, example 4.7, it is explained how to use signal flow graphs to find the output reflection coefficient \$\Gamma_{out}\$ of a two port network. The expression for \$\Gamma_{out}\$ turns out to be independent of the value of the load impedance, however, I am confused as to how this can be reconciled with the fact that  \$\Gamma_{out} = b_2/a_2\$ and \$\Gamma_{load} = a_2/b_2 = 1/\Gamma_{out}\$ , making the value of \$\Gamma_{out}\$ completely determined by that of \$\Gamma_{load}\$ and consequently by the load impedance \$Z_L\$.
Thanks in advance.


texts: Help with connecting two passive speakers to a 3.5mm stereo jack

texts:
Help, I want to learn how to repair my speakers. I have a 2.1 system (subwoofer + 2 stereo speakers) which sounds really great and it would be a shame to lose it as I've grown fond of the sound, and it's also an older model, difficult to replace.
So, it's a subwoofer with a center channel, that has an input 3.5mm audio hole, and an output 3.5mm jack hole for a cable that goes directly into the 2 speakers.
   +   -         +   -
    \ /           \ /

all 4 ends meet in a 3.5mm jack
So far, I know each speaker is passive, and has positive and negative wires. My question is, what is the proper connection for all these 4 cables (left positive and left negative) (and right positive and negative) that should be soldered into a jack so as to sort out whether it's the cable that stopped working. I ask this, because each speaker works perfectly fine on its own if plugged to a source.
Also, the subwoofer/amplifier can deliver stereo, since I plugged my headphones into the stereo output hole and both channels sound alright, but when I plugged the original speakers with the original cable, only one sounded, or when I soldered them a different way into the plug, I get right channel on both speakers.
Help! What's the proper connection for the 4 cables from the 2 speakers into a stereo jack?


texts: Advice for PCB layout 230V AC to 18V DC with another function (beginner continued)

texts:
I am continuing a thread Beginner's second PCB circuit design: AC to DC

Does this PCB design look better than the previous and do you understand it?

I also want to know if the terminal blocks are placed in the correct direction. How should one layout the components such as op amp etc?

The relay is a acts as a switch for a 230V heater which is also connected to the mains 230V.


texts:
I was given this problem by my prof and his answer is simply that it is a parallel RLC circuit and he uses $$s^2 +\frac{1}{RC}s+\frac{1}{LC} = 0$$ for the characteristic equation. It seems to me that it is invalid and when I try to find the solution using differential equations and either nodal analysis or mesh I can't seem to arrive at this solution.
Am I wrong on this "standard" characteristic equation is only valid for a circuit where the three elements are parallel and in this case the inductor and resistor are in series and thus it cannot be used?


texts: 12V 120V inverter and battery for off grid oxygen

texts:
I have an oxygen concentrator that is 120V. The data plate says 3.0 amps and the specs say 280 watts. My question is this. I want to use it in an RV off the grid but without running my generator all night. I have two Interstate 12V AGM batteries I think they are rated at 75 amp hours each.

If I use an inverter will these batteries be enough to power this unit for a full night? If so, what size inverter do I need? Sorry about the basic nature of this question but I am an electronic dummy.


texts:
I got this question and it might be really easy but its just something I have been wondering about I can't seem to be able to find the answer.

When my baud rate in X-CTU isn't the same baudrate as my Xbee module, it asks for a reset of the Xbee module. When I set the baudrate right it doesn't ask for a reset.

Now my question is: Does the Xbee module turn to the default baudrate for a short period of time after a reset or is it able to connect with reset because of other reasons?

So basicaly why is it able to connect using a reset? So what happens in the first period of time the Xbee module is powered on that causes the X-CTU to be able to connect to it?


texts:
I would like to get a PC to flash seven LEDs in response to program events.  I plan to use the parallel port which is provided on the motherboard I am using by a Fintek F81866A "super i/o" LPC chip http://pdf1.alldatasheet.com/datasheet-pdf/view/459084/FINTEK/F81866A.html.  The datasheet describes the parallel port data pins as "TTL level bi-directional pin with schmitt trigger,12 mA sink capability, 5V tolerance.".  It seems to also indicate its 3 volt logic level, see table on page 20.

I beleive I cannot sink current through the pins because I have no (easy) access to a 3.3V supply from the motherboard.  I do have a 5V supply from the front pannel header so I thought I would source a small current from the pins then use some sort of buffer chip to drive the LEDs from the 5V supply.

Because the data sheet does not seem to specify a maximum source current from the data pins, I think I will have to assume that the current avalible is extreamly low to stay safe, say 500uA maximum. I would like to drive a wide range of LEDs, up to say 25mA forward current from the 5V supply.

So I am trying to find a suitable buffer chip.  I have looked at the ULN2003 darlington array but the data sheet says (if I am reading it correctly) that the input current will be up to 1.35mA at 3.85V, so this may be a bit high.  Plus, if the input voltage is down around 3V, will the transistors even turn on reliably?

So what is a suitable buffer chip to use?  Something with very high input impedance to draw negligable current and that works reliably at 3V logic levels and can switch around 25mA on the output.  It also needs to be avalible in a through hole package for hand soldering.

I know I could use discrete transistors but a compact board layout/low component count is important for this application.


texts: Need help with series-parallel resitor networks

texts:
If I have a parallel resistor network with different values for each resistor, how do I calculate the total resistance?
Sorry I dont have enough rep to post pics so I'll try and explain.

Lets say I have a matrix of 9 resistors total in a 3x3x3 grid with
3 different values for the 9 resistors, say 10 ohm, 20 ohm and 30 ohm.
So that makes 3 sets of 10, 20 and 30 ohms.

I need to calculate the total resistance of the 9 resistor network.


texts:
Why is that without the power amplifier block connected to the output of preamplifier, the output signal is ok around 17 volts peak to peak, but if i now connect the power amplifier, the signal somehow attenuates down to around 75% smaller.
This is schematic from pre amplifier block

and the power amplifier block

notice that they are connected by the "ww" connector


texts: How to measure body temprature and HBR with just one IR transmitter and receiver

texts: I want to measure body temperature and heartbeat rate only with a IR receiver and transmitter. How could I do that? Is it an accurate method? Or I have to use IR temperature sensor for this.


texts: Board components that are sensitive to soldering heat

texts:
I have to test the various components of a board after manufacturing. I was told that SRAM, for example, is particularly sensitive to the soldering heat. What are other sensitive components?

The board comprises of an ARM Cortex M3, with USB, Ethernet, GPS, SPI Flash, PSRAM, SIM card and SD card.


texts: Using a different op-amp model for the project

texts:
I have a project to complete and i have been told to use the MCP602 Operational Amplifier, but since that model is nowhere to be found where i am living, i wonder if i can use two LM741 op-amp instead? does is really matter to use the exact same chip for the result?

Apart from number of pins, package & etc of op-amps, are the output gain of all the different models the same? (Assuming a constant configuration of resistors, caps & etc).

Sorry for the very basic questions, thanks in advance.


texts:
i tried to flash the LED of this controller:

http://www.cnx-software.com/2015/01/18/one-dollar-development-board/ (as you can see, there is a led connected to PD3)

with this code:

http://pastebin.com/nCevevxN

but it doesn't work. What am i doing wrong?


texts: Microchip RN4870: Can I create a custom GATT Characteristic Descriptor?

texts:
I am reading through the RN4870 user guide documentation to try and work out how to implement a HID GATT Service.

When I look at GATT specification viewer for the HID service, specifically at the "Report" characteristic, it appears to me I need another Characteristic Descriptor that is not the Client Characteristic Configuration Descriptor (CCCD). I need a "Report Reference Descriptor" as well. However, the CCCD cannot be created in the RN4870. According to this document:

  If we take a close look at the Heart Rate Measurement characteristic, we notice that it includes a Descriptor. That descriptor is the Client Characteristic Configuration Descriptor (CCCD). From our results of the LS command, we see that we have four lines of characteristics; one of those four, specifically the second one, is the CCCD which was added by the RN4870 automatically.

So it seems that the CCCD is added by the RN4870 automatically whenever you indicate that your Characteristic will need to be Indicated or Notified over GATT.

However, I need no commands in the manual to declare any other custom Characteristic Descriptors. And, without that, I fail to see how I can create a HID over GATT service using the RN4870 module.

My questions are:

Is there any way to implement a "Report Reference Descriptor" defined in the HIDS spec with an RN4870?
If not, is there any other Bluetooth module provided by Microchip which does allow that?

Cheers and thanks in advance for your time!


texts: Reason for stepped pins on M12 circular connector

texts:
I've been looking at M12 circular connectors for a project I'm working on (for example this one, drawing here), and I've noticed that many/all of them have stepped pins that create a 3mm or so offset/gap between the connector and PCB once soldered in place as per the datasheet/drawing. What is the reason for this?

A secondary question is, is there any reason not to make the holes in the PCB bigger to make the part flush, allowing for a stronger joint and higher rigidity without the gap? I've been looking around but can't find anything explaining why it's there.


texts: How to calculate power requirements of LED matrix, per row or per LED?

texts:
I have built an LED matrix (9x9) and want to run it with Arduino. I am using technique of scanning, lighting up 1 LED at 1 time.

The more I am reading about power requirements of a matrix the more I am getting confused. As per my understanding, there will only be 1 LED lit at any given time (and it will remain lit for a delay of 300ms). Therefore, I need to calculate voltage and current limiting resistor according to just 1 LED. 1 resistor will be attached with each row. Some articles are suggesting that it needs to be calculated for 1 whole row...WHY? I cant digest the logic.

Please note that I do not intend to use any shift registers or current sink devices. Arduino alone. As also depicted in Arduino CookBook and certain other resources.


texts:
I would like to build a IoT project which needs need 5V.
I have some 6V 1w solar panels which I would like to connect in parallel to charge some LiPo batteries 3.7V

https://www.ebay.de/itm/6V-1W-Solar-Panel-Module-DIY-For-Light-Battery-Cell-Phone-Toys-Chargers/352161541865?hash=item51fe76aee9:g:r2AAAOSwk6ZZsrqC

I have some TP4056 modules which has a max. input voltage of 5.5V
https://www.ebay.de/itm/5pcs-5V-MICRO-USB-1A-Lithium-Battery-Charging-Protection-in-one-Board-Module/351493712096?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

1: What is the best way to bring the 6V from the solar panels down to 5V. A buck converter or a diode 1N4007?

2: Can I charge 2 or more batteries from one TP4056 module or do I need one for each battery?

3: Can I use different size mAh batteries in the circuit?

Thank you in advance


texts:
Context :

Building a wireless sensor based on ESP8266 + DHT22 (+ "X-8266" board) + DHTtester example progam I fell on a rather strange and annoying problem :

Problem :

When powering up the board it doesn't detect the DHT22, unplugging and replugging the VCC pin of the DHT22 solves it.

My 2 cent :

Do you have any clue on this behavior and, better, a solution ?
I could bind the VCC pin to a free GPIO and use it as a 3.3V power source but this wouldn't be very practical ...

PS. I have several DHT22 and the problem is the same for all. Hence I don't think this is linked to the DHT22 by itself, yet I might be wrong as they are all from the same batch


texts:
I illustrated what my circuit do as you see. Switching frequency is 800 Hz. When I increase the load, a noise is heard from my circuit.

Here is my drain oscillocope view in frequency domain. What can I do to eliminate this noise?

Maybe I need a low pass filter but I couldn't know where I'm gonna put.


texts: low impedance as GND and current measurement, applied voltage sharing the same lead

texts:
(Image 1 is for the general idea, image2 is for questions 1 and 2, image 3 is for the 3rd question)

In the setup shown below, the tuning fork is driven by an AC voltage source being connected to one prong and its current output is measured by a current amplifier connected to the other prong.

I looked up the specifications of a current amplifier such as this.  It says "input impedance (DC, Z // 15 pF)     50 Ω - 70 kΩ."

So my question is the following,

If the input impedance of the current amplifier is low enough, can we basically treat it like GND and just not connect the ground side of the AC voltage? This would allow me to connect one prong of the fork to the AC voltage source via one cable
I am not sure how to read the spec of the input impedance.  Is it saying 50 Ω  for DC and 70kΩ  under different conditions?
This diagram shows the tuning fork electrically excited with each of the two wires connected to either of the prongs. (one wire, one prong)  Then, there are cables from preamplifier to the tuning fork (again one wire, one prong).  I am not sure how this configuration would work.  Wouldn't current be split and hence the output of the current amplifier will not give you the accurate reading?


texts: Can a bad USB-C PD charger puff up a battery?

texts:
I have a notebook which supports USB-C PD charging. I've been using 3 chargers that I have. The battery that came with the notebook (original) puffed up after about 1 year of usage, but I didn't seem to know why. Then I bought a brand new battery and started using only 1 charger because I left the others somewhere else. The new battery started puffing days after I started using the other USB-C charger.
Since USB-C Power Delivery is a standard for charging, I thought at least the notebook is able to negotiate the right current voltage etc for charging. All the 3 chargers support the right voltage (19v) and power (45w or up).
Is it possible that this second charger is causing this problem? By the way, why do batteries even puff up?


texts: How to find Polarity and Start End point of transformer?

texts:
I am using ST's eDesign Suite for designing power supply. The suite helps with circuit, BOM and transformer design specs.

I contacted the transformer design firm to get my transformer designed. I gave them all the information regarding the number of turns and length of wire etc..

They are asking me the polarity of transformer and also start, end pin connection of windings.

Being an amateur in transformer designing, I am unable to find any relevant information for above query.

Need Help with that.

Here is my power supply specs

Input: 100 Vac - 265 Vac - 50 Hz - Operating Vdc [98.7 V - 374.8 V]
Output Power: 14.96 W
Out 1: 17 Vdc (35 mVpp ripple) - 880 mA max - 14.96 W - Regulated
Switching Frequency (fsw): 60 kHz

Transformer Information :-

Circuit :-


texts:
I am looking at an old exam question and I am wondering giving a certain G(s) how can I choose the points of the zeros in a PID Controller to have a second order response for small values of K and a first order response for large values of K. So far I have found the transfer function but I am unsure how to determine the zeros. If anyone could even provide an explanation I would be very grateful!

For a) finding the transfer function I get

From here I can see that if K is small I will get a second order response, and if K is large I can see where I would get the first order response.

What I do not understand is how do I find the Zeroes (a and b) for the PID to give the desired response?

Edit:
I apologize, both K and k are the same I will fix that. In the question for small K the system should have a second order response to a step input and a first order response for large values of K.


texts: fully operational PLC with old pc using parallel port for inputs and outputs

texts: hey there I am looking all over the internet for something like an OS (operating System) or either a software that can be programmed as we program a PLC. and for inputs and outputs we use parallel port using flipflops we read and write the inputs and outputs either 16bit or 8bit.


texts: Can i charge 18650 single cell using buck converter?

texts:
I get some 18650 cells from old laptop battery. Cell voltages are good and seems healthy. I want to use this cell as a battery pack for some of projects. I add  protection circuit to prevent short-circuit undervoltage. But i dont have proper charger for this.

Now  is it ok to by charge from other sources. I have buck converter with CC/CV pot. Can i charge 18650 cell by set th CC(~4.2V) and CC(0.4C ~1000mA)?

Do i have to take extra safety steps while charging or is it ok if i can just control Voltage and Current?


texts:
simulate this circuit – Schematic created using CircuitLab

I have bought the LM78H12K 12V voltage regulator, for the 12V output. My input voltage is 17 V DC, but unfortunately this component is not working as expected.

I have uploaded an image of the module. I read the datasheet but with those instructions I am not able to get 12V output, output is showing me 10V only. What and where I am connecting it wrong?

I was looking for a simple circuit for 12V 5A circuit from a 17V AC 20A transformer.  The 78h12k looked like a simple solution for me as I am not concerned about regulator efficiency.

I am using below circuit for the regulator, but this gives me only 10V output and the regulator does not gets hot.

Please refer to the datasheet.


texts: Methods for increasing output power and efficiency of a ZVS flyback driver

texts:
I have built the following ZVS driver:

I am using this circuit at a resonance frequency of 150kHz.

My hope is to be able to modify this circuit for wireless power transmission. With that being said, I will only be applying a maximum of 20V DC to this circuit at the input. From testing the circuit with that voltage, the output power is very low, barely turning on a small LED light. Can anyone request any ideas for changes or modifications to achieve better output power?

I am new to building circuits so any help would be appreciated.


texts: What is Soldering temperature of STM32F303 IC chip 100-pin?

texts: I want to solder a 100-pin STM32F303 IC on a PCB. What is the recommended soldering temperature? I could not find it in the datasheet.


texts:
Maximum switching current of this relay at 250 V is 10 A.  Why is the maximum switching current at 30 V also 10 A?  I wonder why it can tolerate 10 A at 250 V but not 80 A in 30 V because the power is the same?

P1 = P2 = 250 V x 10 A = 30 V x 83 A


texts:
We are trying to develop a wired sensing network that will have up to 200 sensors attached to it, spread over what could be 100 m. There will be one main controller that uploads each sensor's information to the cloud software. This is because there is no Internet connection. Thus, we are forced into using a 4G mobile data system.

I currently have a 24 sensor network setup with a Raspberry Pi, but it uses I²C as the communication method (GASP, I know) and so is definitely not scalable in any way shape or form.

My question is around what would be the industry recommended protocol for communicating between the sensors and the main controller. Ideally, the main controller will not be required to poll all of the sensors to check if they have more data, but rather each node would push this data to the main controller. My current thoughts are leaning towards CAN. However, would this decision be future-proof?

I am going to give a brief overview of why I was thinking CAN. If you could please correct any of my misconceptions, or add more information it would be much appreciated. I also will add my thoughts on using other wired/wireless networks and why I don't think they will work:.

CAN

Built-in collision detection
Multi-master built in
ISO protocol
Fast (1 Mbit/s)
Future-proof due to its prevalent usage in industry.
Expandable (no extra hardware required to add a node)

Ethernet (LAN)

All sensors to have power of Ethernet capability.

Lightning quick
All sensor modules would require more expensive hardware for the Ethernet stack
Would require a large switch infrastructure for many bays
Every new module would require running of more cable
Distance may be a problem for Ethernet

Bluetooth

Each sensor has its own Bluetooth connection.

Range is too limited. We could create a mesh network, but the close sensors would have a large throughput of data.
Limited number of connections to the main controller (20 max)

Wi-Fi

Each sensor has its own Wi-Fi chip.

Increases cost of the sensor hardware
Require a power router to have that many connections
Setup becomes an issue as there are no inputs on the sensors
Range of the Wi-Fi is usually not up to 100 m.

RS-485

A multidrop; however, this is just a simpler version of CAN in reality.

1-Wire

I think this would be a joke trying to use this, but I am open to suggestions.


texts: MC33269ST-5.0T3 Voltage Regulator, does it exist?

texts:
I'm trying to implement an Arduino MEGA board into my PCB that I'm designing and I've come across a part on the schematic, MC33269ST-5.0T3.  I can't seem to find it anywhere, and it isn't on digikey.  The closest I can find is this here, but that is a 3.3 volt regulator: https://www.digikey.com/product-detail/en/on-semiconductor/MC33269ST-3-3T3G/MC33269ST-3-3T3GOSCT-ND/2120818

Inspecting my Mega board that I have sitting on my desk it would appear to physically be the same package, and ON Semiconductor doesn't appear to make a 5V version in that type of casing, but I'm wondering if it is at all possible that it is a documentation error, or an obsolete part?

In any case, does anyone know where I can purchase this part, or an equivalent?


texts: Is there a device to get modulo of voltage value?

texts:
This may sound very naive and impractical question, and most likely the answer is negative, but still: is there any more or less simple (simpler than ADC/DAC) analog component or circuit, which makes modulo operation on the value of voltage, given Vref?

For example, if Vref = 1V and input V = 11.56V, then the device will produce 0.56V. Similarly, with Vref=2V, the same input will give 1.56V. Of course, Vinput must be from some sensible range.

If such a thing exists, then it can be used to make a new(?) type of ADC.

UPDATE: I am aware, that modulo function (applied to time) is just a sawtooth http://en.wikipedia.org/wiki/Sawtooth_wave , so there may be some solution involving linearly turning voltage to time period, then reading the sawtooth value.


texts: Bipolar signal amplifying to high voltage

texts:
I have a bipolar (+-15V) square wave with a frequency of approx. 600 kHz. I want to amplify it to +-500V (not precisely), 50W. The load is around 1kOhm.
Can anyone give me an advice on how to do it?


texts: Is there such a thing as a Schottky zener?

texts: I was thinking about this when I was looking for over- and undershoot protection. If you use a zener you can clip the overshoot at a defined level (ignoring the slowness of the zener), but the undershoot will leave something like 0.7V. A Schottky diode would half this to 350mV. So, is there a Schottky zener which takes care of that, or do I have to place a common zener and a Schottky diode in parallel?


texts:
Why is the neutral point of the alternator hooked up to the earth which makes all the voltages of the lines with reference to the earth. Doesn't this makes us more risky to the shocks?

I think we use earth as a return path in case of AC,Is it true??.

Why don't we use a configuration with a separate neutral wire(not hooked to the earth) for the return path of current,which makes less chances of shock(in that case we will have to touch both the live and the neutral wires to get a shock).

I have this doubt for a long time,I googled it up but it has made me more confused.
I'm sure you will get me out of it.
Thanks..


texts:
I was thinking of creating a surveillance mobile robot. And I am having a problem of choosing a PIC or a Arduino microcontroller. The surveillance mobile robot is controlled via wireless fidelity (Wi-Fi). If I choose PIC, is there a need for an Ethernet module?

I have searched that it need it for an Arduino board to connect to the Internet. I am a bit experienced with PIC, but some say Arduino is better for beginners. Which is better: using Arduino or PIC for the project? Or it should be done with both Arduino and PIC? And also I am thinking of using an Android phone as the controller for the robot.

What should I do?


texts:
I've found ferrite beads work great for eliminating high frequency noise on the input and output of DC-DC converters, but now I have a DC-DC converter that is outputting 20A and ferrite beads work at a maximum of 10A (and not great that high). What are my options?

The switching frequency of the converter is 350kHz and the high frequency noise I'm trying to get rid of it above 100MHz, differential noise. I need a board-mount solution that is not huge and ideally not custom-wound. Should or could I put a bunch of 10A beads in parallel?


texts: What does 'PLS' acronym mean on this CAD drawing?

texts:
I was making some EAGLE parts and was curious about the highlighted acronym shown in the image below:

What does it refer to?

Full Datasheet


texts: Does only wiring 2 poles of a 3 pole overload relay have any effect?

texts:
When wiring a single phase starter, they tend to jumper the overload such that all phases of the overload are used.
Now, considering that the overload has 3 separate bimetal strips all connected to the same tripping mechanism, it shouldn't matter if you only connect 2 or even just one phase through that overload.

As I was reading up on this, I saw the terms "phase balance" come up a lot. This is understandable, but is this a feature of all thermal overload relays? Will they all trip if current isn't balanced through all phases? If not, then why can't we just wire one phase through the overload relay, in the case where we only have a 3 pole overload, that is.


texts:
If I connect this very small load (3 LEDs) to a mains to USB adapter, it's fine. Full brightness, great.

I can't even measure the current it's so low.

However, if I connect it to my PC it does 3 things:

It flashes a bit from bright to dim, stays dim and windows says it's malfunctioning.

Nothing has shorted out or anything like that, so is there a minimum current I should be drawing from a PC's USB port?


texts: How to buffer balanced (XLR) audio signal while forwarding phantom power

texts:
Background:
I have a condenser microphone, which requires +48V phantom power from my mixing desk. The microphone has a source impedance of "<200 Ohm" as per manufacturer. As you may recall, phantom power is delivered over both the "+" and "-" wires in the XLR connector, put on the wire with a 6.8 kOhm resistor pull-up on each wire. This means the maximum amount of current that can be drawn is about 14 mA (into a short) and more realistically < 10 mA. Some of this power is used by the built-in pre-amp in the microphone data sheet says 2.5 mA.
I've built an inline mute switch using a DPDT switch (rated for +48V DC) where the "mute state" switches the phantom power over to a blinking LED, reminding me I'm on mute.
Unfortunately, because this is a mechanical switch, AND because of the phantom power, switching on/off makes for loud pops. Given that I want the blinky-LED to consume some current when in the "mute" configuration, I probably need to switch off the pre-amp in the microphone to have enough current available -- and, anyway, I do need to turn off the signal from the microphone for it to be "muted."
With that background, I believe that I need to build some kind of active/solid state circuitry to mute/un-mute the microphone, turn on a blinking LED when it's muted, and still pass phantom power to the microphone. It's the last part that has me somewhat confused. Because the original source of the phantom power is already resistively protected with high impedance, how do I best re-buffer the signal, yet carry the phantom power forward without too much power loss?
I've considered extracting the common mode power with a center-tap transformer, and then using my own opamp to re-buffer the signal (which I can then turn off when needed) but this feels quite inelegant as I add another couple of high-resistance resistors in the path of the power. Yet, I don't know how to pass the power without also passing the signal any other way.
Here's an example sketch of what I have so far:

Microphone on the left, mixing desk on the right.
I'm looking for suggestions on how to better accomplish the separation of signal vs phantom power, ideally in a way that doesn't require adding more inline high-resistance resistors.


texts:
I've a FPGA design ( I didn't write a single line of sources code) and I've to add a module ( in the design there is a Wishbone bus where it's possible to link others wishbone interface ). The modules linked to the bus are UART and "custom UARTS", there are 16 devices linked to the bus.

In my opinion the design is written really bad ( a lot of long combinational path linked to the wishbone, memory element not registred and a writing code style really caothic and far away to the hardware implementation ) but "it works and close the timing" without my module ( the clk constraints is 125 MHz and the PAR get 125.109 MHz with an occupation of resources of about 50% more or less ).

When I add my module the timing aren't met in several paths. The slow paths are outside my module. Now the question, can I be sure that the problems isn't my module ? Is the PAR report a sufficient way to prove that the problem is the others part of the design ?


texts:
First question here

In my system, a LT3652 IC should drive a solar panel with these specifications:

Voc = 9,94V
Vp = 8,54V
Vmp = 7,95V
Isc = 0,90A
Wp = 7,15W

to charge a 3,7v Li-Ion battery at 2A max.

To select the inductor, it has been suggested me from a user:

  "Select an inductor of 10uH capable of 2.5 to 3A. E.g., Bourns p/n
  SDE0805A-100M. It is tricky to calculate ripple current for a solar
  panel, because Vin max does not occur during Iout max. But 10 uH
  should give you low ripple current"

I would like to know if this formula in the datasheet can help me how to calculate L. It is:

  $$L= {\frac{10\cdot R_{SENSE}}{\Delta_{I(MAX)}}}\cdot V_{BAT(FLT)} \cdot
\left[1-\left(\frac{V_{BAT(FLT)}}{V_{IN(MAX)}}\right)\right] (μH)$$

  In the above relation, \$\Delta_{I(MAX)}\$is the normalized ripple current, \$V_{IN(MAX)}\$is the maximum operational voltage, and \$V_F\$ is the forward voltage of the rectifying Schottky diode. Ripple current is typically set within a range of 25% to 35% of \$I_{CHG(MAX)}\$, so an inductor value can be determined by setting \$ 0.25 < \Delta_{I(MAX)}< 0.35 \$

\$R_{SENSE} = 0,05 \text{ }\Omega\$
\$I_{CHG(MAX)} = 2 \text{ }A\$
\$\Delta_{I(MAX)} = 0,5 \text{ }A\$ (25% of \$I_{CHG(MAX)}\$)
\$V_{BAT(FLT)} = 4,2 \text{ }V\$
\$V_{IN(MAX)} = 9,94 \text{ }V\$

Hence:

$$L=\frac{0,5}{0,5} \cdot 4,2 \cdot \left[1-\left(\frac{4,2}{9,94}\right)\right] (μH)$$

$$L= 2,44 \text{ }μH $$

Is this formula correct to estimate the inductance?

- EDIT - BOUNTY REWARD

In the datasheet it is also mentioned that inductors also need to meet the volt-second product requirement. Is this parameter important? I calculated: $$V_{SEC}= -1,34 V\cdot \text{ }μS$$

from this formula:

$$V_{BAT(FLT)} \cdot \left(\frac{1-V_{BAT(FLT)}}{V_{IN(MAX)}} \right) (V\cdot \text{ }μS)$$

Why this specification is not listed in the vendors' datasheets?


texts:
We have 230 VAC power supply in our lab.A chemical earthing is done for this power supply. I have connected a SMPS (LRS-35-12) to it. The Output of SMPS is connected to a load of maximum 2A. I have measured the smps output voltage as 12VDC and the device (load) is working and controller is sending data also. But at the same time I have turn my multi-meter at AC voltage mode and measured the SMPS output voltage,I found it as 25VAC. (I expected it to be around 0 VAC.)

So, what could be the reason of it?


texts:
I got new wall mount AC Adapter, the adapter itself is good, but cord is low quality, very short (1m) and very hard and coarse, non-flexible. I want to replace adapter cord with better one. The adapter have ABS case without screws, two halves possibly are glued or thermo-welded together.
Does anyone know whether it's possible safely and accurately open such plastic cover with knife and replace cable? I just don't want to damage the item in any way. I can try to return adapter to but its looks difficult.


texts:
I am trying to find the drive level of an OCXO. The OCXO I am using is the OCXO.
I am trying to find the max drive strength. I find only the minimum peak power in dBm. The screen shot is as shown below -

Now, how ca I find the max or peak power ?


texts: Determine by the order of transfer function what kind of filter

texts:
How can I determine by looking at the following tranfer function, that is this the transfer function of a band-pass filter:

$$\frac{1}{as^3+bs^2+cs+1}$$


texts: Thevenin equivalent of voltage divider bias

texts: Can anyone explain to me the step by step procedure in finding out the Thevenin equivalent of the Voltage-Divider bias shown.


texts: What is this component? It's between two ICs, probably on a communication bus. One is a microcontroller and the other is some sort of memory. It's as small as an smd capacitor or resistor.


texts: What is actually meant by "parallel paths" in a simplex progressive lap winding of a DC Generator?

texts: Many of my textbooks mention "parallel path" term, but I am unable to actually understand it. Also along with this it would be quite helpful to know, how the polarity of brushes is determined?


texts: Data storage interrupt when shorting the CAN bus

texts:
In the MPC5674 microcontroller, when creating a short circuit in the CAN bus, the controller is getting restarted repeatedly.

The root cause of this reset has been found to be due to a 'data storage interrupt'.

What is the data storage interrupt? And why is it caused when creating a short circuit in a CAN channel?


texts: Why is this simulated transistor turning on at such a low voltage?

texts:
I'm trying to simulate (using the Mouser edition of MultiSim) a very basic transistor circuit, above, with a MOSFET acting as a switch. It sort of works, inasmuch as V2 reads 20V when V1 = 0, meaning the transistor is not conducting; and reads  20mV when V1 = 5V, so it's conducting very well.

My problem is that it seems to start conducting at a very low voltage. Even at V1 = 0.05V, V2 = 20.3 mV. If I'm reading this datasheet that Mouser provides correctly, it shouldn't start conducting until V1 hits the threshold voltage, somewhere in the 2-4V range. Is that interpretation right? And if it is, what's going on in this circuit?


texts: Why is the collector and/or the base current of a transistor independent of the voltagesource of the collector?

texts:
I have a water valve which should be operated between 6-12V. I want to control this with an "standard" arduino-transistor switch (see image below, change the motor to a valve).

When trying to calculate the base-resistor needed, I use these basic formulas

$$ I_b = I_c/\beta$$ and $$R = \frac{V_{cc} - V_{be}}{I_b} $$

Since the data-sheet for the valve says it needs 320 mA @ 12V, and Vcc = 5v (voltage from arduino) and Vbe = 1.2 (my bc337 transistor), I can calculate that R = ... (something)

However, these formulas does not say anything about the collector voltage. What would happen if I choose 1.5v, 5v, or 12v etc ? If I change the voltage supply to the valve, shouldent the collector current change accordingly?

Extra question: can I in some way destroy/burn the aurdriono pin with this circuit?


texts:
I am in the process of designing a new ADC\DAC PCB with a digital interface and analog front end. I have tried to separate the different grounds in my circuit to reduce the noise as much as possible but I am not sure if I what I am doing is correct. Please see the diagram below

I have tried to ensure that all the GNDs are returned via a single return - anGND -> GND -> GND RETURN 1\2.

Should I separate my digital GND (route it to GND Return 1) from my analog ground (route anGND to GND return 2)? NOTE GND Return 1 & 2 are connected directly at source.
Should I give my +/-12V LDO a different ground?
Should I give my +5Vadda LDO a separate ground?
Should I incorporate an additonal "digital" GND for the +5.3V DC\DC ?

In previous designs we have used the same DC\DC +3.3V->+1.1V and have not seperated the digital and anlog grounds and it has worked fine. Here do you think I should seperate them? If yes which grounds would you recommend?
What other recommendations do you have?
I am not sure why my diagram above can't be viewed. I have re-inserted it below as a jpg:

I changed the design slightly as below:


texts:
I have a Raspberry Pi outputting a 3.3v DC square wave that I'd like to be able to amplify to just under 20v, the maximum the piezo can handle. Just to clarify, the piezo does not have an internal oscillator and the Pi is outputting at anything from 50Hz to 3kHz to make audible tones.
From looking elsewhere online, there seem to be many different approaches to amplification but most require an AC wave to work.

I'd like to be able to simply and cheaply amplify the wave generated by the Pi to make recognisable musical tones with the piezo as loud as possible. The wave doesn't have to be perfect, but I'd rather there was as little interference or noise as possible!
I have 3.3v, 5v and 7.2v available on the project and I could add a pair of 9v batteries if 18v is needed.
The piezo has a 7kohm impedance, if I remember according to the data sheets, if that helps.

A circuit diagram would be good but a bit of an explanation to go with it would be preferred!

Edit: The data sheet is at http://www.farnell.com/cad/356850.pdf

Another edit: I'll be testing Spehro's answer as soon as I can, assuming that school has all the extra components needed.


texts: Input offset voltage, input bias current, input offset current of operational amplifier

texts: Are operational amplifier parameters such as input offset voltage, input bias current, input offset current DC noise? Can I get rid of these noises by using a high-pass filter? If not, how can I get rid of these noises?