texts: Is my SAMD21 bricked due to a wrong clock configuration from software?

texts:
I use a SAMD21 without an external crystal, by using its internal 32kHz oscillator and transform it with DFLL to 48 MHz.

The processor wakes up normally with GCLK0 on 1 MHz, so I first activate GCLK1 with 32 kHz, switch the processor to it so I can turn off and reconfigure GCLK0 to DFLL 48 MHz, and then switch the processor back to GCLK0. (this is the same method the Arduino Zero does, with the single exception that it uses the external 32k resonator, while I use the internal one)

I now have GCLK0 running on 48 MHz and driving the CPU. I also use the generic clock 2 on 1 MHz for PWM, UART, and other things. So far so good. I debug it with SWD, with the use of an XPlained Pro board where the microcontroller has been removed and the SWD lines go directly to my board.

Everything worked fine. Until I wanted to set up the generic clock 3.

REG_GCLK_GENCTRL = 0x000003;  // disable gclk3 to allow changes
REG_GCLK_GENDIV = 0x000103;   // set division to 1
REG_GCLK_GENCTRL = 0x010603;  // activate gclk3 with 8 MHz

After uploading the software, the microcontroller became unresponsive and I can no longer access it via SWD.
I had a spare board, and foolishly tried it as well. The same thing happened.

The error says

  error: Could not activate interface, but found DAP with ID 0x....

It suggests erasing the flash and names deep sleep as a possible cause. I can erase the flash successfully. However, no other operation is possible.

My first guess was that I somehow messed up the clock settings, the CPU needs a running clock to be able to be accessed via SWD, and it cannot do so for the lack of a resonator. So I took out the resonator from the XPlainedPro, and installed it into my board the exact same way it was in the XPlainedPro, including its capacitor.

It didn't solve my problem.

I've seen this error in a few threads, but usually it's about JTAG not working while SWD continues to work.

I there a way to save my controllers, or are they bricked?


texts: Off-Grid Inverter causing a GFCI trip when charging EV

texts:
I have a transformer-less, 48VDC to 120/240VAC inverter that is off-grid. I have a 120VAC GFCI outlet wired to the inverter. When I plug my 120VAC EV charger into the outlet, the GFCI trips. It does not trip when I plug my laptop in. It does not when I wire the same GFCI outlet to the grid and charge my EV.
Why does this happen?
Could I add anything to prevent the GFCI trip? According to NEC it would need to be a class A 5mA trip GFCI.
Edit: It's a 12K Sol-Ark inverter. The battery is floating. No PV attached to simplify the problem. The inverter has a built-in ground bus bar. Neutral to ground bond is installed between the built-in neutral and ground bars.


texts: What do the line-and-circle symbols mean on these electric meters?

texts:
I was looking at an electrical installation and came across unfamiliar symbols on the front of a pair of meters.
These are from three-phase 240v meters running on a timed system. One each for peak/off-peak usage.
On the first image, I recognise part of the lower row:
indicating 50Hz frequency,
Unknown symbol
Double insulated
CE safety mark
I don't however recognise the line-and-circle symbols nor the ratchet-type symbol. I have been unable to find search terms to even start looking them up?
My best guess is that it has something to do with supported wiring schemes for the meters.
Can anyone shed some light as to what these are called and what they mean?
Thank you.


texts: Mouse Wheel Rotary Encoder ... encoding wrong

texts:
OK, guys - I'm pretty confused here.

I bought a cheap wireless mouse to gut and use in a project. Right now I'm trying to get the rotary encoder behaving, but (while it IS behaving) it's behaving oddly. If we call the pins 1, 2, and 3, in the mouse circuit board, 1 is joined in a solder blob with the casing, and that's all tied to +3v. 2 and 3 and hooked to individual pins on the IC.

I'm trying to figure out the pattern for the encoder so I can detect which way it's spinning, but that's where I'm getting confused. If I measure the resistance between 1 and 2, it alternates every "click" of the encoder/mouse wheel. However, when I measure the resistance between 1 and 3, it toggles the exact same. The resistance between 2 and 3 toggles the exact same as well. I would I expect one of the pins to be "on" for 2 clicks and "off" for 2 clicks to provide 4 unique "addresses" on the encoder, but that's not happening.

Am I missing something? Suggestions welcome.


texts:
I have an inverter for cold cathode lights powered via a molex connector from a PC power supply, with a PCI/PCI-E slot bracket where is placed an ON/OFF switch, and I would need to use one light at a longer distance, exactly at a distance of 7 and half metres. There is a 2-pin connector leading to the inverter. From what I have read, cables leading to a cold cathode from the inverter hasn't to be long, so it seems like that the only option is by using a 2-pin extension cable. Can it be used like this and if yes, what wire I need to use for it? Assuming there isn't such extension available to purchase, can I cut the cable and solder the wires to create an extension?

Some more information:

Input voltage of the inverter: 12 V

Output voltage of the inverter: 680 V

Current draw: 5 mA


texts: How to check if sync signal is inverted?

texts:
in input of a CPLD, I have a syncronization video signal that can be like this (positive polarity):

or like this (negative polarity):

I want to recognize the type of the sync signal and invert the signal only if it has positive polarity. How can I do this with digital logic and without using analog filter?

Thank you


texts: Miniaturizing home automation help? [Novice]

texts:
Right now I am doing a home automation project and I want to create two things. The first is a device that looks like this but has the capability to also be controlled over wifi using Arduino. I know the Arduino route, but the final product is clunky. This device is really big and I was wondering how I could make it smaller using relays. Is there another device that I could use?

The second project is to replace and old wall socket with a newer one that has 2 USB ports and 2 outlets that could be controlled through Wifi communication. I am lost here. I understand how an outlet works with the 3 wires, but how would I be able to create a system that can take the command ("on/off").

Can I use the belkin WeMo to learn more? Any help at all will be great.


texts: How to use ATmega328 SPI with a 31 bit shift register

texts:
I'm using an Allegro 6280 PWM LED driver for a project. This is a cool little IC except for the fact that it is a 31 bit long input register.  This is no problem if I simply loop through my 31 bits and set the pin states accordingly, but I'm wanting to use the atmega's on-board SPI to speed things up a bit (the 6280 requires an external clock source for it's 10 bit long PWM cycle).

The 31 bit long register looks like this in my application where R,G & B indicate the 10 bit PWM values for the attached LEDs.

0BBBBBBBBBBGGGGGGGGGGRRRRRRRRRR

These shift registers are chainable, so I've built a linked list to represent them:

struct Pixel {
  uint16_t red;
  uint16_t green;
  uint16_t blue;
  Pixel *next;
};

So, the idea is to set the latch pin low, iterate through all the Pixels and then after sending the last one set the latch high to latch the data into each register.  This would seem easy except that due to the uneven length of the register I have to construct nasty-looking code to be able to loop around to the beginning again so that it never sends any empty bits. Also, the latch might need to happen after an arbitrary number of bits are transmitted, not just the last one.

Does anyone have any ideas on how to get this done, or am I simply barking up the wrong tree and stuck with manually twiddling the pin states?

Thanks.


texts: Can aluminum-housed resistors be used as dummy load for battery testing (etc.)?

texts:
I want to buy me one higher-quality resistor to have a durable and stable dummy load element suitable for use in battery testing and other purposes.

I've come across a 100 ohms / 10 W one which is aluminum-housed and not too expensive.

From its physical specifications, would this make a good dummy load?
I really want to buy one in good quality, as you would normally buy such thing once in your life and keep it in your equipment; moreover, it is way more convenient to operate with something that is about the size of your hand than to mess with alligator clips with a tiny 1-cent carbon resistor.


texts: How does VHDL handle bitwise operations?

texts:
I'm having a problem in some VHDL code I'm writing. I want to drive a signal with two other signals AND'd together like this:

mysignal <= "010" and '1';

The result I expected was a bitwise AND, resulting in mysignal receiving the value of "010". Instead, I got a compiler error telling me "No feasible entries for infix operator "and"."  When I try:

mysignal <= "010" and "111";

it compiles. Is it possible in VHDL to do a bitwise logical operation, without having to alter my signals and make them all the same width?


texts:
I am looking for some material (books/sites) related to embedded system programming in C language.
Here in the lab we have available three plataforms: one Microchip PIC18f4550, one Freescale HC12 and one ARM (Beagleboard).

We are willing to teach embedded C with the PIC, assembler with Freescale and embedded operational systems with Beagleboard.  Each class will be a six month course.

Open to all advices.

Thanks


texts: Desoldering SMT components with a reflow oven

texts: I'm wondering if it's possible to desolder all smd components on a PCB using a reflow oven? My plan is to hang the PCB upside down over a piece of aluminum foil, use a standard reflow profile and let gravity do the work. Saving the components is not a concern, only desoldering them. What would prevent this plan from working? Will surface friction prevent some of the smaller components (e.g. 0402 or 0603) from dropping?


texts: Why does my AVR act weird (resets, data corruption) when receiving a few bytes on the UART?

texts:
I have an ATmega644 connected to another device using the UART. After receiving a few characters on the UART the device resets and/or acts weird. Some examples of this behavior:

Code before the main loop is executed again but MCUSR is 0 (i.e. no "real" reset)
Code inside the main loop is executed even though the switches connected to the inputs were not pressed (pullups are configured properly).
Sometimes the MCU just hangs
Sometimes ports that were not configured as outputs act as outputs (e.g. LEDs connected to them light up even though the DDR for that port is 0).

The device is using an external 18.432 MHz crystal and the UART is set to 19200 baud. It is powered with 5V; the RX pin is connected to a 3V3 RPi.


texts:
I've searched the Net to find a decent software that would give me phasors plots with stacked phasors (for adding , subtracting phasors etc), such as the image below, but I couldn't find it. I tried in Matlab sofware but nothing fits my problem.

Does anyone of you has a suggested software for my problem?

Thanks.


texts: Should the vias for decoupling capacitors touch the pads of the capacitor or not

texts:
The board in question is a four layer board, with a dedicated ground plane as well as a dedicated power plane. Capacitors are MLCC, imperial 0402 (metric 1005). MCU is an STM32.
The question now is how to combine decoupling capacitors and vias. The best way would be to use plugged via-in-pad, but sadly for this project this is out of the question.
So now the question is whether I should a) connect the vias and with the pads of the capacitdor with traces (for superior manufacturability but inferior impedence) or whether I should b) place the vias so close to the pads of the capacitor, that no traces are needed.
Regarding a):
When I leave something like 0.2 mm of distance between the annular ring of the via and the pad of the capacitor, there will be solder mask between the annular ring and the pad of the capacitor. This solder mask will prevent solder paste getting sucked away from the pads of the capacitors, down the vias.
See the 2010 article "Five Via-In-Pad Myths" from cadence.com: "That little mask dam will stop solder from flowing into the via and everybody will be happy."
The downside: due the relatively long traces, the inductance will be relatively high.
The following picture shows a capacitor (imperial 0402/metric 1005), a 0.2 mm wide trace, a 0.6 mm diameter via (hole size: 0.35 mm) and 0.2 mm distance between the annular ring and the pad of the capacitor (the mask dam mentioned above):

Regarding b):
The second option could lead to problems during assembly (solder paste getting sucked into the via) but will have superior inductance, as the annular rings of the vias overlap with the pads of the capacitor. No traces are used. See the 1997 article "Bypass Capacitor Layout" by Dr. Howard Johnson: "series inductance is impacted favorably by ... vias jammed up next to the pads (no traces)".
See this picture in which the right edges of the via holes line up with the left edges of the pads of the capacitor:


texts: How can I debug microcontoller code during run time?

texts:
I'm using Nuc240 Microcontoller which has its UART0 configured for 'printf',I use a UART to USB controller to view the output on screen. This works during run time also, so that I could monitor things during run time after exiting debug mode.
But is this the best method or is there any other alternative methods available?
Also I use IAR Embedded workbench and the Terminal I/0 is not showing the output in 'printf', what could be the reason for this? I'm using NuLink-Pro as debugger.


texts: A confusion regarding signed representation of binary numbers

texts:
Suppose I have an ADC that converts the analog input samples to 4-bit signed binary numbers. The resolution of the ADC is 0.5V. Since the binary o/p is of sign magnitude representation, the MSB has no magnitude and the i/p range of the ADC is from -3.5 to +3.5.

However there are two representations of 0 (i.e. if the i/p is 0V). One of them is 0000 and the other 1000. That means for 0V, I have two different encoding levels. How do I represent that on the voltage characteristics? Its pretty clear to me for positive values, how the characteristics is going to be like -

Where do I put the level 1000? Obviously 0000 and 1000 cannot be present at the same place.

Also, if the i/p is 2.7V, the encoded o/p is 0101. Similarly for an i/p of -2.8V, going by the previous logic, shouldn't the o/p be 1101?

This is the question that got me thinking about it -


texts:
In this question I am referring to this article.

At first I was looking for a physical explanation of the fact that energy or the signal, respectively, travels much faster through a wire than the electrons inside of it do (drift velocity).

After reading the article, I understand that neither the amount of current flowing around, nor the voltage between two points is responsible for the speed of the energy transfer. It’s rather the material surrounding the conductor that’s affecting the propagation speed with its permittivity and permeability. Is this correct up to here?

Figure 4, however, makes me wonder two things:

Of course, every point of a conductor has the same potential and inside of conductors, there won't be an electrical field. But why is that? You learn that since we're inside a conductor, a current will work against every potential difference that might exist between two connected points, thereby compensating it. But isn't current (the actual flow of charge carriers) incredibly slow? And doesn't this make an immediate compensation impossible?
Now let's say two connected points will always have the same potential. When talking about RF engineering, you learn that as soon as the wavelength becomes of the order of the physical wire's length, you will measure different voltages across one single wire. How does this correspond to the idea of an immediate response of the charge carriers?

What am I missing?


texts: When is it safe to ground DC- (specifically audio output)?

texts:
With regard to audio devices, if all equipment is unbalanced and there are no DC- connections to earth ground, equipment will generally operate hum/noise free despite large common mode voltages between earth and audio signal+/-. With balanced audio devices, all chassis are connected to earth ground and to each other via cable shields.  Properly designed balanced inputs/outputs use differential signaling and "equal" impedances between internal signal commons of each device and signal +/- , rejecting common mode noise.

When interfacing unbalanced to balanced equipment, say a laptop or cell phone audio source being charged by a switching supply to a balanced input audio amplifier, the large CM voltage difference between devices often introduces hum and noise into the signal.  One solution to this is using an isolation transformer, but I’ve found that the hum can still be audible, and that the best solution to completely eliminate it is additionally to earth ground the signal common coming from the unbalanced device.

I’m wondering, however, if there are cases where earth grounding the audio signal common out could cause issues and even damage equipment.  If there already exists an earth ground connection internally at the power jack for example, but the audio signal is powered through bridge rectifiers, chokes, etc. then earth grounding the output signal common would force two different parts of the circuit that should be at different potentials to be at the same potential.  Measuring my laptop switching supply output, for example, which has a 3-prong plug, I get a resistance of 1kOhm between the laptop chassis and earth prong. In that case tying the signal to ground directly doesn’t seem like it would be an issue, since the two circuit commons (power and audio signal) can still be allowed to be at different potentials (correct me if I’m wrong).

Not being entirely familiar with difference switching supply topologies, do most wall-warts and brick switching supplies have their DC- output isolated from earth ground/neutral (or connected through a resistance/etc.) or are there supplies that do connect these? And/or is there a foolproof way to determine if grounding the audio out signal common of a switchmode powered unbalanced device (laptop, phone, ipad, etc.) is safe and not likely to damage anything?


texts: Voltage drops are not adding up to voltage of the source

texts:
We did an experiment using a very simple circuit shown below:

The voltage drops over each resistors were: 4.9, 2.8, and 2.2 respectively. According to the rules the voltage drops across each resistor must add up to the voltage of the source, which in this case was 5 V, however this is not the case. Why is that?


texts: How can the maximum average power transfer be negative in a power delivery circuit?

texts:
It is possible that the Thevenin resistance \$R_{Th}\$ of a circuit is negative. This occurs in non-linear circuits. Likewise, in AC circuits, the real part of \$Z_{Th}\$ can be negative.

For AC power transfer, \$P = \frac{1}{2}|\mathbf{I}|^2 R_L\$, or
$$P = \frac{1}{2}\frac{|\mathbf{V}_{Th} |^2 R_L}{(R_{Th} +R_L)^2  + (X_{Th} + X_L)^2  }$$

It is well known[1] that the power is at a maximum when \$X_{Th} =-X_L\$ and when \$R_L=R_{Th}\$. This leads to a generally well known equations for maximum average power transfer:

$$P_{\text{max}} =\frac{|\mathbf{V}_{Th} |^2}{8 R_{Th}}$$

Unfortunately, if \$R_{Th}<0\$, this yields negative power. It also implies that \$R_L<0\$, which also does not make sense.

How to find the maximum power for such a circuit?

Edit:
The maximum is found by taking two derivatives, \$\frac{\delta P}{\delta X_L}\$ and \$\frac{\delta P}{\delta R_L}\$, and setting them equal to zero. For \$\frac{\delta P}{\delta X_L}\$, it is easy to see that \$X_{Th}=-X_L\$. For \$\frac{\delta P}{\delta R_L}\$, the derivative is:

$$ \frac{\delta P}{\delta R_L}\ = \frac{|\mathbf{V}_{Th} |^2 R_L[(R_{Th}+R_L)^2-2R_L(R_{Th}+R_L)]}{2(R_{Th}+R_L)^4} $$

This to find the maximum, we set \$\frac{\delta P}{\delta R_L}=0\$. The resulting equation simplifies to:

$$R_L = \sqrt{R_{Th}^2}$$

Mathematically, this has two roots, \$R_L = R_{Th}\$ and \$R_L = -R_{Th}\$. Both seem physically unrealistic to me; the positive root give a negative power; which doesn't make sense for a passive element. The negative root gives an infinite power transfer, from:

$$P = \frac{1}{2}\frac{|\mathbf{V}_{Th} |^2 R_L}{(R_{Th} - R_{Th})^2   }  =\frac{|\mathbf{V}_{Th} |^2 R_L}{0}$$

This implies an infinite power transfer, which would be great, right? But I'm not sure how realistic that is either.

[1] For example, section 11.3 in Fundamentals of Electrical Circuits by Alexander


texts: Electronics interface circuit for PIN Photodiode

texts:
I am designing an interfacing circuit for PIN photodiode which will be used in NIR spectrophotometer project. The PIN diode is IG22x250S4i and works in photovoltaic mode. The specifications are:

Capacitance (@0V): 40pF
Forward Voltage: 0.56 V
Reverse Voltage Max: 5V
Forward Current: 1 mA Max
Reverse Current: 0.5 mA (Max)
Dark Current: 0.5 uA (at 5 V reverse voltage)
Shunt Impedance: 400 - 500 k ohm
Wavelength: 1150 - 2200 nm

The datasheet of the sensor is over here. The application notes and reference circuit is over here.

Initially, I tried connecting a 10 k ohm resistor in parallel to the diode and observe the response in a oscilloscope. I was getting 500mV max when the light source is bought near to the diode. Rather, I realized that due to 50 ohm impedance of probe, I was getting much smaller signal.

Later, I picked a random op-amp (input bias current in 100 pA) and designed the circuit similar to the one given below (with jumper wire):

I was getting rail-to-rail signal (3.3V) with that op-amp but it was very noisy.

I have now moved to designing a PCB with an opamp. I have read this document and considered selecting an opamp with low input bias current, low input offset voltage.

But I am confused with bandwidth and slew rate of the opamp for my application. My setup has a single PIN diode and a stepper motor. Light after passing through the sample and lens fall on grating. The grating splits the light and falls on the diode. The motor moves to capture the whole spectrum. The time required to capture the spectrum is 1 seconds and 3000 points will be taken in that interval. So, one sample will be around 333.3 us. If I hypothetical consider a peak in spectrum causes an instantaneous jump of 0 V to 3.3 V (of photodiode output) in single point (out of 3000 points), then maximum rate of change of input voltage (to opamp) will be 0.0099 V/ us and that's how i concluded the slew rate of opamp should be more than 0.0099 V/ us.

I am not confident about my calculation and are looking for similar calculations to calculate required bandwidth of the opamp.


texts: How does one change Vivado IP signal types?

texts:
The Xilinx IP block called Utility Buffer allows the designer to convert one single-ended signal to a differential signal pair (among other things).

However, the block expects the input and output ports of the block to be of type 'clk', which then causes these signals to use clock routing resources instead during implementation.

I have attempted to edit the source code outside of Vivado, but Vivado is somehow forcing type 'clk' on these ports anyway.

Is there a way to force these ports into a certain type? Is there a workaround?


texts: Hall effect sensor output type - open collector vs RC

texts:
I am about to select a hall effect sensor. Two types are available: one has an open collector (OC) output, the other an RC output. The datasheet states that both are current sinking. But because I neither know what the RC output is (at least I am not sure) nor how it works, I am not able to select one.

My question is about the RC output. Does RC stand for resistor / capacitor to create the output signal? If so, how does it work? My guess would be, that the resistance or capacitance are modified to create a varying output signal.

Because I have to choose between the OC / RC output type I would like to know the advantages of the RC output type. The datasheet only mentions:

  If there is stronger electromagetic interference or the distance between sensor and the measuring
  instrument is farther,  an OC output (open collector) is suggested to use.

Why should I choose the RC output type?


texts: Running an Arduino off an AC Circuit with a Bridge Rectifier

texts:
I am having an issue running an Arduino (requiring a 3.3V power input) from a 21V AC circuit. The input of the circuit is from a doorbell transformer and provides 21V AC. Then the AC input passes through a bridge rectifier to produce a DC output (of about 26V). The output from the bridge rectifier is smoothed with a capacitor, and then a voltage rectifier converts the ~26V input into 3.3V output for the Arduino.

However, this circuit has an issue I am having trouble figuring out. Measuring the output of the 3.3V voltage regulator reveals that it is, in fact, outputting 3.3V as expected. However, the Arduino seems to reset itself over and over.

My working theory at this point is that the issue has something to do with the connection to ground. If I disconnect the AC input and replace the 3.3V regulator with an external, regulated 3.3V supply, the system works fine.

I would greatly appreciate any help you could provide with diagnosing the issue with this circuit design.


texts: Extract sound file from electronic answering machine

texts:
I have an AT&T Model 1738 digital answering machine and I want to record the sound from one of the messages. The speaker in the answering machine is low quality, so I do not want to just play the message and use a microphone because that would result in a low-quality recording.

I would rather collect the audio information from some point before it gets amplified and sent to the speaker. What would be the necessary equipment and general procedure to do this?


texts: Transformer of my Power Supply in LTpsice

texts:
Can you help me on how to model or calculate the inductance of a step down transformer which supplies 230V to produce 0V-15V in LTspice I'm really confused.

Below is my circuit which I want to make the transformer for, I've already built it in practical and its working but in LTspice its giving me headaches.

Thank you.


texts: Speaker for crystal radio rather than sensitive piezoelectric speaker Crystal radio

texts:
I am a science student of grade 8 and  researching and learning about radio waves.

I am currently trying to make a crystal radio. The problem I am facing is  the speaker I have to use for the project.

I searched on the internet regarding the same and found that there are high sensitive piezoelectric earpiece that most of the people use for  crystal radios, but in my locality I could not find them.

So I also tried using piezoelectric buzzer for my project but it failed to produce sound.

what kind of speaker should I use?


texts: What is the typical max voltage for sound card line in?

texts: What is the typical max voltage rms, peak and peak to peak for a sound card line in?


texts:
I'm wanting to power a USB device through the USB connection with some kind of solar cell arrangement, separating the data and power lines. I currently connect the +5V/GND USB lines to a constant voltage source, and it provides 270mA but this could vary with other configurations.

I'm quite new to solar cells, so getting a bit lost in the basics. If I used something like this, listed as 100mA at 6V, if I connected that directly to the +5V/GND lines on the USB connector, would the current supplied follow the IV curve at 5V and supply about 110mA? Or should I use some additional components to get a regulated 5V supply?

Assuming this is the case I would need 3 of these in parallel to provide the 270mA required, but then would the cells drive ~330mA through the device instead? Or will the device only draw 270mA from the cells?

Thanks for any help.


texts:
Briefing:

Trying to drive a 3V motor with gearbox, using TM4C. Motor specs are given below.

First tried with 2N2222A, later plugged motor directly in to LF33ABV voltage regulator. On both setups, motor was quite weak and wasn't moving properly even under small loads. I guess it was because of the 0.5A current limit of the either components.

Then I checked the components at home and found BDX53C power transistor, which can supply up to 8A. After some calculations, here is the setup I'm planning to build. "A" will be connected to one of the TM4C's PWM capable ports.

If I don't burn something else then I will later build another setup with 555 timer & potentiometer to replace the launchpad.

Edit: Forgot to mention that, "A" is connected to Port A5 of the TM4C. Both TM4C & battery grounds are connected to each other, although it is not seen on the drawing.

Question:

Is it safe to use BDX53C on this setup? If not, can you suggest some components to buy?


texts:
I have an LED Controlled by a signal to its cathode. If I make the cathode Low, LED Glows, and if cathode is High, LED is OFF.

The voltage applied at LED Anode is always 12.5V.

I observed that, when I turn ON the LED,

Voltage at LED Cathode = 0V

Voltage at LED Anode = 2.1V

LED Glows

And,
If the voltage at the cathode is made high,

Voltage at Anode = 12.5V

Voltage at Cathode = 11.2V

LED Doesnot glow.

My question is, in my second case, when the LED Doesnot glow, why is there a voltage difference between the LED Cathode and Anode?

I understand that in the second case, the voltage difference between the cathode and anode is not greater than the forward voltage of the diode which is why it is not glowing. But when it is not glowing, why is there a voltage difference between the anode and cathode?


texts: How to rinse container used for ferric chloride etching?

texts:
From what I have gathered online, after etching one stores the "used" ferric chloride (more specifically FeCl2 and CuCl) in some container which can then be taken to a waste disposal facility.

What about the equipment you use? For example the container in which the PCB is soaked in? Can you rinse this container out in your sink? Or are you expected to use a new one each time and take the old one to a waste disposal facility?

What about rinsing the board itself? Can you rinse it out in your sink (white porcelain, stainless steel), backyard? Or are you supposed to rinse it  and keep the contaminated water to later take to a waste disposal facility (along with the container that held the rinse water)?

What do people do? This part is glossed over in every tutorial on PCB etching using ferric chloride that I've come across =/


texts: Could someone help me understand this simple circuit?

texts:
This is a single-wire earth-return telephone system used in cave rescue communications.

simulate this circuit – Schematic created using CircuitLab

The ground is a metal casing to make contact with the users hand. Line is clipped to an exposed section of a wire that runs through the cave.

The circuit is shown in receive mode, PTT switches to transmit, the speaker serves as a microphone and speaker. All systems I've seen use a Rocking Armature Transducer for the speaker. There is no base station or similar - you can just connect two or more of these to the same wire and use them.

My electronics knowledge is not good enough to fully understand this. Here's what (I think) I do understand.

C3 and C4 are audio coupling (block direct current flow.)
R1 and R2 hold + of the op-amp at 4.5v.
Earth-return is a misnomer - it actually works off the capacitance of your body.

When receiving

R3 is shorted and therefore does absolutely nothing.
The op-amp is working as a buffer and does not amplify the input.
I'm guessing C1, C2 and R4 are serving to filter the input - perhaps suppress high frequency noise.

When transmitting (this is where I really get lost)

C2 is now shorted and does nothing.
What's R3 doing - is the op-amp now amplifying?
Are C1 and R4 still performing some function?

Am I right so far? Can someone please help me understand the rest?

My goal is to be able to alter the circuit to try out different speaker setups.

Thanks


texts: Pull-up/Pull-down resistor connected to op amp input

texts: In the circuit below, I understand that R1/C1 and R3/C3 are low pass filters. But I don't get why the pull down resistor (R2) at U1 input and pull-up (R4) at U2 input. Are they just to set a known output in case the inputs are left open?


texts: Help identifying a component on an old computer PCB

texts:
I was hoping someone may be able to identify this component in an old (80-90s) computer.  I have both the schematic symbol and a photo of the actual component.

Further to that, how would I identify any associated value since it has nothing printed on it except a yellow band (does that convey much information?)

In context:


texts: motorcycles and vehicle ground loop detectors

texts:
I have been asked if it is feasible to make a motorcycle accessory that will trigger the traffic ground loop antenna sensors that typically fail to register the motorcycles presence. Reading up on these sensors, I find that they detect a vehicle by driving a signal into a loop and measuring a change in frequency due to the inductive skin effect from the metal in the vehicle over the sensor.
This makes me wonder if it might be possible to build a low power transmitter to drive an antenna mounted directly under a saddlebag to force a change in the ground loop operating frequency actively, as opposed to the change registered from the passive inductive skin effect.
The only antennas I have made so far have been from following ARRL guides to the letter.
So I am hoping that someone might be able to detail what the antenna and loading coil construction would be and its drive requirements to accomplish this.
Some of my references are:
http://www.editraffic.com/wp-content/uploads/loop_install_guide.pdf
http://www.marshproducts.com/pdf/Inductive%20Loop%20Write%20up.pdf
http://www.editraffic.com/wp-content/themes/eberle/flash/loopCalculator.swf
http://www.fhwa.dot.gov/publications/research/operations/its/06108/02.cfm


texts: Voltage drop on each diode - connected in series

texts:
I have a question regarding the voltage drop across a diode when it is connected in series with others. For example, I will use the following exercise:

Each diode has Vd = 0.7 V, id = 1mA and n=1. I need to calculate the value of R so that the voltage on node V1 equals 3. I have the answer to this question but I do not understand how the voltage drop across each diode is calculated to find the current through them. Any help is appreciated. Thanks a lot.

simulate this circuit – Schematic created using CircuitLab

Answer:


texts:
TLDR; how to make a MIDI input withstand shorting to \$\pm12V\$?

This is a counterpart to this question, I'm asking this as I was inspired by the great answer I got there.

I'm designing a MIDI input in a eurorack modular synth module on a TRS jack (this is a semi-standard non-standard way to save space), where it's quite possible for the user to accidentally plug in anything between ±12 to the input. I obviously need to protect the input, while keeping the circuit maximally compatible with other MIDI devices.

The standard MIDI input circuit adapted to the TRS connector:

simulate this circuit – Schematic created using CircuitLab

where tip, ring and sleeve are of course the pins of the TRS input connector. The LED represents the opto-coupler, which is in this case a 6N137. The MIDI standard really just specifies a 5mA current loop as the signaling method, and gives an example circuit.

Now, assume that the user plugs in say \$+12V\$ on the tip and \$0V\$ on the ring. Then the current through the optocoupler and resistor is 46mA, which is just within absolute maximum for the 6N137, and gives a power dissipation of 500mW in the resistor, so a not-impossible-but-hefty 3/4W resistor will survive. The situation is the same in the reverse voltage case.

However, it is not impossible (although requires a stereo lead which is rare in the eurorack environment) that the tip could be at \$+12V\$ while the ring is at \$-12V\$ (or vice versa), giving a total voltage difference of \$24V\$, in which case the absolute maximums of basically all the components is exceeded.

The reason I'm having difficulty coming up with a nice protection circuit is that:

the circuit should be floating, to maintain the opto-isolation
Because of this, I can't clamp things to ground or the power rails etc
the usual driving circuit on the other end is just a simple two-resistor "current source", so the voltage drops introduced by diodes tend to throw things off.

Since the \$\pm12V\$ case is quite unlikely to happen by accident, I'm considering just keeping this circuit as is, with R1 a 3/4W resistor, but if there's any nice way to protect against \$24V\$ I'd be very interested in hearing that. Bonus points for staying a bit further clear of the absolute maximums of the components, and of course the circuit should be maximally compatible with the various MIDI output circuits out in the wild.


texts:
I am trying to create a circuit to allow me to switch a project on and off with the activation of a momentary switch (a momentary push button or reed switch, for example), but I'm coming up blank and need help.
I have a few parameters:

Source voltage is 5v DC
Output load is less than 1mA - It's just driving the Enable lead on a chip (Consonance CN5711)
Output voltage should be as close to 5v as possible
The circuit must be "default on" - when power is first applied, the circuit needs to be on; actuation of the momentary switch would turn the circuit off and leave it off until the next time, and repeated actuation would cycle that (I hope that makes sense)
Must draw as little power as possible.

I have a working example of what I need in front of me but the company that made it used several unmarked components that I can't identify and is not willing to provide me that information, so I have to design my own.
Let me know if there's anything else you guys need.
Thanks


texts: Measuring voltage between two points...wirelessly?

texts:
I want to measure voltage between points A and B. Let's assume that there's some obstruction/difficulty in simply attaching cables between those points. Is it possible to measure the voltage wirelessly somehow?

I had an idea of a device that measures voltage at some point with reference to an on-board stable potential S. Let's say two such devices are attached to points A and B:
Device 1 measures voltage between A and S
Device 2 measures voltage between B and S
Measurements are then transmitted wirelessly to a server. Is it possible to "substitute for S" and recover voltage between A and B?

Thank you in advance for your answers :-)


texts:
I'm trying to read the temperature sensor from the LSM303C. I have enabled the sensor and can see the values move when the temperature is changed. But, the format of the sensor data is not provided by any data sheet or resource I can find on the web. Does anyone have this information?

Thanks in advance.


texts: Switching buzzer on and off with two transistors

texts:
I want to make a simple water level indicator with tank full alarm as shown in the diagram. What I want to achieve is, when the tank is full to 100% and water is still flowing through the inlet pipe (ie, the pump is on) the buzzer should beep. I have two outputs from IC ULN2003 for that- Pin 14 switches on when the water level is 100%  and pin 15 switches on when water is flowing through the pipe. Also, I want the buzzer to stay off as long as the above-mentioned conditions are not met. Now my questions are,

1) Is the circuit right on the transistor switch side? If not, is there any other
   circuit (preferably simple) which I can use?

2) Is transistor 3906 good enough for this use?

3) The resistor values, are they okay?

4) Should I give a reverse bias resistor to the transistor base as shown in the
   the second diagram (R2)?

simulate this circuit – Schematic created using CircuitLab

]2]2


texts: Context of Li-Ion MnO2 "Cell Configuration" Specification

texts:
My application supports variable pack configurations: 4S4P, 4S6P and 4S8P.  Each one obviously uses a different BMS profile, and other minor changes such as charge/discharge MOSFET and fuse selections.

Data sheets for Li-Ion cells vary widely in terms of the specification parameters supplied, but the critical parameters are always given.

However, specific to (some) Sony (now muRata) 18650 VTC-series specs, such as the VTC6 and VTC5a data sheets, they list a "Max Cell Configuration" parameter.

Please note that these are not listed as test configurations (all other specifications pertain to the single cell).

Please also note that other Sony cells of the same MnO2 chemistry and similar DCRs do not specify this at all.  In fact, no other manufacturers of high continuous discharge current 18650 cells, with even higher ESR specify "Max cell configuration" at all.

For the VTC6 (DCR=30A, Zcell=18mOhm) the parameter is called "Max Cell Configuration", and is spec'd 5S2P.

For the VTC5a (DCR=35A, Zcell=18mOhm) the parameter is called "Cell Configuration", and it is spec'd TBD.

I have not found this specified for any other 18650 cell by any other manufacturer within 30% similar capacity & DCR.

I presume this spec surfaces due to the very high DCR of 30A for the VTC6 (35A for the VTC5a).  However, I can find no case of battery packs being limited in terms of the parallel or series pack configurations -- not in terms of a cell's specifications -- just in terms of BMS, wasted heat, partitioning protection and management circuits, etc.

Even if I use a VTC5a, it does not seem to me that "TBD" is even a valid specification, given they could come back later and stipulate 3S1P or any other arbitrary max cell configuration -- if that is important, should they not all have this parameter specified?

My question is, am I going to fail BIS, IEC, CE, or any other certification because of this specification, limiting me to 2P only?  If I point it out, I will fail.  If I do not point it out, I am liable.

BTW, I did try to get information from both Sony and muRata on this topic, to no avail, despite our intention to mass produce this product.


texts: Why Does DC Load Draw Twice As Much AC Current Through Transformer?

texts:
I have designed the following circuit, comprised of 4 loads, 1 of 4.2ohms and 3 of 21ohms, drawing a total of 2.4Arms (1.5A, 300mA, 300mA and 300mA respectively) of AC current through the secondary of a transformer which outputs 6.3Vrms connected to the mains voltage (120Vrms) through the primary.

However, I have found myself in the need of feeding the last load with DC current instead of AC, so the solution is to add a rectifier and then connect the load to it to draw DC, naturally, adding a ripple filter capacitor and dropping resistor to adjust for 6.3VDC, taking into account the 1.1V drop of the bridge (datasheet).

I have a book on the subject and the author has also a website, and in both he mentions that whatever DC current the last load is drawing will count for twice as much AC current (so a load drawing 300mA DC counts for 600mA of AC) for the transformer, but he doesn’t explain why (I guess it’s obvious?).

Does this mean that the last load along with the rectifier can be substituted for a single load that draws AC current but with half the resistance? Why is this?

My thinking process is that all the rectifier is doing is re-directing the current so that it always flows in the same direction through the load, both in the positive and negative swings of the AC current before it, in my opinion, the transformer should not even know that there is a rectifier, from the transformer points of view there is always a fixed value load drawing current, in any polarity.

I ran a circuit simulation in EveryCircuit without the capacitor and drop resistor and the waveforms match my conclusions, orange is the AC current drawn by a 21ohm load, blue is the DC current drawn by the last 21ohm load after the bridge and green is the AC equivalent of the current drawn by the last load through the bridge.

The DC current after the bridge is the same as the AC current before it, except for the polarity, I don’t understand the difference in current compared to the loads drawing AC though, 420mA peak vs 308mA peak, maybe the crossover distortion due to the bridge?

But still, the current drawn per cycle is the same, it’s just that after rectification the current flows only in one direction, so I don’t see where this extra double current would be going ¿?

If I add the capacitor the waveforms match what I have read, it turns the current drawn into brief spikes instead of more somewhat constant lobes, is this where the extra current is going? But even then, my analogy is that the shape of the curve is like a rope with a fixed length, you can re shape the rope from a sinewave to a square wave or into thin spikes but the length of the rope can’t change because that would mean the area below the curve would change meaning more or less current is being drawn, right?

And if  P=V*I and the voltages are fixed, an increase in current would mean an increase of energy per second being consumed but where does this energy go?
There is power lost in the bridge and the drop resistor but I don’t see how this would mean a double increase in current drawn.

The reason I’m focusing on current and not voltage is because I need to find a suitable fuse to add between the last AC load and the rectifier, as well as to find a suitable fuse for the primary, I’m aware of current inrush and I will add a thermistor to the circuit later on, but right now, I need to know the steady state current values. So, for the circuit with only AC loads that would mean 2.4A but how much for the circuit with the DC rectified load?


texts:
I'm trying to build my own mechanical keyboard. Everyone uses Teensy as for as i can see. I wanna use PIC18F2550 instead. I'm using CCS C btw. The problem is, i can't send more than 5 bits at all. Tried to send different arrays, they collide somehow. Increasing report count from "usb_desc_keyboard.h" doesn't work. "usb_puts" function didn't work either.

When i send multiple arrays, one by one, PIC sends key characters. No problem there. But it doesn't make the same response as a regular keyboard. Normally, first type takes longer time than others. This way PIC sends characters continuously. I wanna send 64 bits together. Is that possible?

I'm using matrix method for button interactions, got no problem there.

EDIT:

I added code. tx_msg array size is 7. I want to increase this to 64.
Found this guy claiming he did it. http://www.microchip.com/forums/m368006.aspx
Gonna try this when i get home.

void usb_keyboard_task(void)
{
   static int8 tx_msg[7]={0,0,0,0,0,0,0};
   static int8 leds;

   if(!input(pin_B0))
      tx_msg[2]=0x04;
   else
      tx_msg[2]=0;

   usb_put_packet(1,tx_msg,sizeof(tx_msg),USB_DTS_TOGGLE);

   //receive NUM LOCK, CAPS LOCK, etc LED status from PC.
   //we won't do anything with it.
   if (usb_kbhit(2))
   {
      usb_get_packet(2, &leds, 1);
   }
}

void main(void)
{
   setup_adc_ports(NO_ANALOGS);
   set_tris_a(0b0000000);
   set_tris_b(0b11111111);
   port_b_pullups(0b11111111);
   usb_init_cs();

   output_high(pin_A0);

   while (TRUE)
   {
      usb_task();
      usb_debug_task();
      if(usb_enumerated())
      {
         usb_keyboard_task();
         delay_ms(50);
      }
   }
}


texts: Total gate charge of a capacitor variation with voltage?

texts:
Here is a picture of the variation of a total gate charge of a MOSFET with voltage at Id=16A,
Can someone explain does it increase with the voltage?


texts: Will "hot plate" reflow soldering work without a solder resist coating?

texts:
With a successful through-hole design under my belt I am now ready to try fabricating a board that uses surface-mount components. I have been reading about this, and have gathered that the DIY crowd has gotten reasonable results with "hot plate" reflow soldering.

I think I understand the basics of this technique, but one point on which I am still unclear is the necessity of a solder resist coating. Is reflow possible without it?

I have seen a kit from LPKF for adding a solder resist coating to a prototype board, but do I really need it?


texts: Common collector amplifier current amplification

texts:
given:

  Re = 500 Ω
  Rb = 261 kΩ

What can we tell about the current amplification? Is this circuit useful?


texts: Heating vacuum tube filament via capacitor

texts:
As I understand vacuum tubes (like triode / pentode) usually are designed to be heated with certain current through the filament.

And usually it is about low-voltage and comparatively high-current. E.g. 6.3 V at 300mA.

Schematics I usually find around use transformer to get this heating voltage. I wonder, whether I can instead connect heater filament directly to 220V AC via suitable capacitor to limit current. E.g. I think 4.7 uF should provide about the said 330mA. And it can feed several lamps in chain.

What could be the drawbacks? I can suppose that temperature will be pulsating slightly (like incandescent bulbs do about 5% light pulsation) and this can affect the anode current... But vacuum tubes have slower temperature time-constant...

UPD: some clarification - this scheme of course should only be considered for isolated filament (how do we call it... indirect cathode heating?).

Also "simplified" calculation I=Uac*(w*C) which I mean is correct only while total voltage on filament (or chain of filaments) is small in comparison to full Uac.


texts: Why the measured voltage increases when I change ground reference?

texts:
The following image shows my connections:

The grounds of all devices are connected to a common PCB. When I measure the 1.2V referenced to the ground on my PCB, it reads 1.201V which is great. But when referenced to the common GND PCB, it increases by 23mV, I expected it to be lower than 1.201V (because of bigger ground loop, therefore more voltage drop) not higher, how come?!

Edit #1 : Notes

I have only ONE voltmeter used for both measurements, sorry it's not clear in the image.
"My PCB" is supplied by 64V from the shown power supply, then it's converted to 12V then to 1.2V

Edit #2 : More Notes

These measurements are the same even before I soldered the rest of the board. I solder power modules first of all, even before a load exists I got these results!
The "common PCB" is a one layer board that is only used as a common ground. It has no ICs or passive components. Only copper pour and holes for crocodiles to be attached.


texts: What do the letters and numbers mean in the addresses of Allen-Bradley PLCs?

texts:
I am using Allen-Bradley Programmable Logic Controllers. And using the Logixpro as a simulator.

In PLC we are talking about counters, timer, math operations( addition, subtraction, greater than, less than), FIFO, FILO, Move. And in this commands they are using the B3, S, R6, and N7.

I am not sure I fully understand what B3, S, R6, and N7 represent. I know that B3 is bit address, S is the status bit, R6 is register, and N7 is register, but where should you use them.


texts:
Why do the two netlists give totally different output impedance values ?

Netlist 1:

*CMOS inverter https://electronics.stackexchange.com/questions/383552/measurement-of-output-impedance-of-a-cmos-inverter
.PARAM V_SUPPLY = 3.3
.PARAM AC_POINTS = 10
.PARAM AC_START = 1000
.PARAM AC_STOP = 1E6
VDD VDD 0 'V_SUPPLY'
VSS VSS 0 0
MP OUT IN VDD VDD P1 W='9.987275E-06' L=3.500000E-07
MN OUT IN VSS VSS N1 W='9.987275E-06/2' L=3.500000E-07
CIN IN VSS 1E9
Rf OUT IN 1E9
IOUT VSS OUT AC 1
.AC dec 'AC_POINTS' 'AC_START' 'AC_STOP'
.OPTION POST PROBE ACCURATE
.include modelcard.nmos
.include modelcard.pmos
.MEASURE AC Zac_power0 rms par('abs(i(vdd))*v(vdd)')
.measure AC ZROUT1 rms par('v(OUT)/abs(i(VSS))')
.end

Netlist 2:

*CMOS inverter https://electronics.stackexchange.com/questions/383552/measurement-of-output-impedance-of-a-cmos-inverter
.PARAM V_SUPPLY = 3.3
.PARAM AC_POINTS = 10
.PARAM AC_START = 1000
.PARAM AC_STOP = 1E6
VDD VDD 0 'V_SUPPLY'
VSS VSS 0 0
MP OUT IN VDD VDD P1 W='9.987275E-06' L=3.500000E-07
MN OUT IN VSS VSS N1 W='9.987275E-06/2' L=3.500000E-07
CIN IN VSS 1E9
Rf OUT IN 1E9
IOUT VSS OUT AC 1
.OPTION POST PROBE ACCURATE
.include modelcard.nmos
.include modelcard.pmos
.control
*AC dec 'AC_POINTS' 'AC_START' 'AC_STOP'
AC dec 10 1000 1E6

let ROUT=OUT/abs(i(VSS))
plot ROUT
print ROUT > ROUT.log
.endc

.END

For exact problem duplication, just copy the two netlists into two different files and run ngspice. Cross-check the terminal output with mine as shown above.

The modelcard.pmos and model.nmos can be found at https://github.com/promach/frequency_trap/blob/development/optimization/inv


texts:
I'm relatively new to PIC controllers and I'm trying to figure out the best ACD operating mode for my setup.

I'm using the PIC32MX250F128B controller and I have two analog input connected to the PIC AN9 and AN10 pins.

I thought the Alternating Sample mode(with auto sample enabled) would be good for me, by connecting AN9 to the PIC's MUXA and AN10 to MUXB. I've set the number of samples per interrupt to 16, but I'm confused how my buffer will store the values. Is it "MUXA, MUXB, MUXA, MUXB..." or something else?


texts:
I'm using a Python program to send some message over serial port to Arduino. This message contains the pin number of the pin and whether it should be HIGH or LOW . Eg: Sending 2H\n should set pin 2 to HIGH.

pins array maps the pin numbers in the messages to the actual pin number of arduino. 1H corresponds to pin 22 on Arduinio Mega.

When manually sending one message at a time, things work fine. However when Python sends a series of 30 such messages one after the other in a loop with no delays, pin 1 is always stuck at whichever value it is set to on the first series of messages.

Example:

1L\n
2H\n
3H\n
4H\n
5H\n
...

followed by

1H\n
2H\n
3H\n
4H\n
5H\n
...

will cause pin 1 to be stuck at LOW when it should be high.

On arduino, this is the code that parse the message and sets the pin values.

void setPinValues(String message) {

  for(int i = 1; i <= sizeof(pins) / sizeof(pins[0]); i++ ) {
    String pinNumber = String(i);

    if( message == pinNumber + "H\n" ) {
      pinValues[i] = HIGH;
    }
    if( message == pinNumber + "L\n" ) {
      pinValues[i] = LOW;
    }
  }

}

void loop(){
    if( Serial.available() > 0 ) {
        received = Serial.read();
        message += received;
        if(received == '\n') {

            // Set pin values
            setPinValues(message);

            // Write to pins
            for (int i = 1; i <= sizeof(pins) / sizeof(pins[0]); i++) {
                digitalWrite(pins[i], pinValues[i]);
            }

            // Clear buffer
            message = "";

        }

    }

}

Arduino Mega communicates with Windows 8 x64 system over USB using a baud rate of 57600. When using a lower baud rate of 9600, this problem is not seen.

Furthermore, at baud rate of 57600, if I were to replace setPinValues with the following code, pin 1 is properly switched on and off.

void setPinValues(String message) {

  for(int i = 1; i <= sizeof(pins) / sizeof(pins[0]); i++ ) {
    if( message == String(1) + "H\n" ) {
      pinValues[1] = HIGH;
    }
    if( message == String(1) + "L\n" ) {
      pinValues[1] = LOW;
    }
    if( message == String(2) + "H\n" ) {
      pinValues[2] = HIGH;
    }
    if( message == String(2) + "L\n" ) {
      pinValues[2] = LOW;
    }
    if( message == String(3) + "H\n" ) {
      pinValues[3] = HIGH;
    }
    if( message == String(3) + "L\n" ) {
      pinValues[3] = LOW;
    }
  }

}

Doesnt both versions of setPinValues do the same? Why does lowering the baud rate prevent the problem? I cannot use a lower baud rate because the USB buffer gets filled up and things slow to a crawl.

To compare the last char H or L:

String pinValueString = message.substring(message.length() - 1);
char pinValueBuffer[2];
pinValueString.toCharArray(pinValueBuffer,2);

if(pinValueBuffer[0] == 'H') {
    digitalWrite(pins[pinNumber], HIGH);
}


texts: Interfacing OLED 0.95'' 96*64 with ATMEL SAMD20 Series MCU

texts:
I am trying to interface my OLED 0.95'' 96*64 with my SAM D20 using SPI interface.

I am fairly new to interfacing, so I'm finding it difficult interfacing the part.

Question:

1) When I provide the 3.3-5V to Vcc and GND, should the OLED display something, or it only does on initializations?

2) I connected the Vcc, GND, SS=0(because MCU is Master), MOSI and SCK pin on the OLED with the respective pins on the microcontroller using the SPI tutorial for the micro as in the second link below.

I saw no activity on the screen, is this an initializations issue. Since it says that the OLED has the SSD1331 driver, do I have to use/send commands that trigger the OLED for it to start.

I thought I should see something on the screen to indicate that it is powered on, I checked the SPI module on the MCU and that seems to be sending out data correctly, however I have not regulated the data.

I would appreciate if someone who has worked on such a project give me a top level outline of steps I should carry out if I am going wrong somewhere.

Also, if it could be a parts error please indicate.

Useful Links:

1) OLED Module

2) Atmel SAMD20 MCU (SPI Documentation):


texts: How to turn-on laptop's battery pack after replacing cells?

texts:
After a few years of use, my battery pack finally died. The laptop doesn't even detect or try to charge the pack anymore.
So I replaced the cells in the pack for new ones, but that didn't make it to come to life again. I tested the pack's end terminals to see if there is voltage, but there is no voltage at all.
If I connect the pack into the laptop, it's not detected either.

The pack has what it seems to be a built-in charge indicator. When I press the button on the left, the first LED blinks for 3 seconds, that's all.

I followed the intructions in here to try to revive the pack:

  Connecting the voltmeter to the outer terminals, take a 100-Ohm resistor, tie one end to ground, and with the other end touch each terminal while observing the voltmeter

But had no success.

Is there something else I can do to bring the pack back to life?

Hardware details:
Laptop: HP Omnibook vt6200
Battery pack: 14.8V (8 x 18650 cells)


texts: Variable capacitor notation with a division sign (e.g. 2÷10p)

texts:
In this schematic, there is an unfamiliar notation for the variable capacitors using and division sign or obelus, for example 2÷10p (red), as opposed to, e.g. 1p for a fixed capacitor (green).

I have presumed that this is used for indicating the number of air gaps in a rotary variable capacitor, as the total capacitance is the capacitance of one gap, divided by the number of gaps (or plates - 1):

\$\frac{C_{one\ gap}}{n_{gaps}} = \frac{C_{one\ gap}}{n_{plates} - 1} = C_{total}\$

Is this the correct interpretation?


texts: disabling internal pullups on D0 && D1 on AT90USB1286

texts:
Can anyone just verify quickly for me that this:

cbi(PORTD, 0);
cbi(PORTD, 1);

will disable the internal pullups on the AT90USB1286? I'm trying to avoid damaging some 3.3V components that I'm communicating w/over i2c. Thanks in advance.


texts: How to connect unused MOSFET from Dual N-channel MOSFET?

texts:
This question may be stupid but how should I connect an unused FET in a dual-channel MOSFET ?
I using this one multiple times on my board but in one case I'm using only one MOSFET. I'd like to know how I should connect the unused one ? I guess I should connect the gate to the source (through a resistor) but what about the source pin ?


texts:
For growing crystals it is important that there are no vibrations. Is there a cheap and easy way to measure vibrations in the floor, like people walking, doors closing etc.?

Perhaps an accelerometer is possible, but those are pretty expensive (Nun chuck is less expensive).


texts:
When you purchase a crystal to use as a clock, the company is asking you exact frequency to set it at.

I remember needing a crystal that was 4x the NTSC color carrier and they were asking me how many digit precision I needed.

What is the process to 'set' the crystal output so precisely?


texts: I would like to have a motion activated IR LED array. I found simple instructions to make a battery operated IR light which would be installed outdoors, but how can I make it respond to motion? I have a motion sensing transmitter and receiver set model #HS3600. Is there a way to make it work with the LED array? Simple instructions for a novice would be really appreciated.


texts:
So far I have just found this paper which provide a guide to achieve that:
MOVING FORTH. Part 1: Design Decisions in the Forth Kernel

Is there a more recent guide?
Which Forth is better for that purpose?

I am planning to use it with PIC16F877A, and I know that PicForth exists, but it is just a compiler, not a system to communicate with a terminal window by a serial connection (that's why I am going to use Forth).


texts: Decreasing phase noise of natural oscillators by passive resonant filter on-chip in the MHz regime

texts:
I was doing a literature research on microwave filters and to me it looks like passive SAW filters/resonators have the highest quality factor below 1.5 GHz, but with a high power loss. Coupled planar coils/stripline (U-shaped) do not really reduce the phase noise in principle, but would be easier to fabricate. Active LC-circuits are probably better.

What about magnetic materials based filter/resonators based on ferrites/YIG/Permalloy and ferromagnetic resonance? Downsides seems to me that ferromagnetic resonance is not present in the MHz regime, rather GHz.

What I need:

between 100-500 MHz phase noise filtering at a distinct frequency, doesn't have to be tunable, as its purpose is to reduce phase noise of natural nano-oscillators with high phase noise
passive and possibly lower loss than SAW
input signal around 0 to -10 dBm and should stay above -20 dBm
below mm² size on-chip
fabricable with laserlithography, dry/wet etching, sputtering techniques

Is the SAW-resonator the best option I have?


texts:
I am trying to switch on and off LED's with the help of a relay.

The relay I am using is 24VDC SPDT relay and the LED is 12VDC LED.

When I switch on the 12V supply the yellow LED should glow since the relay is in normally closed condition[please refer the schematic] and when the 24V supply is turned on the relay gets activated and becomes normally open thus allowing the flow of current to turn on the red led. Eventually, cutting of the supply to the yellow led.

When testing this circuit on a breadboard, the yellow is turning on when 12V supply is given and when I turn on the 24V supply, the relay gets activated but the red led is not glowing. When I measured the voltage near the led[supposed to be 12V], it is not getting any supply itself. I am stuck at this point and don't know if I am missing any small thing here.

The relay I am using is G5LE-1-E DC24 RELAY GEN PURPOSE SPDT 16A 24V.


texts: Light Dependent Resistor Photoresistor LDR: gl5516 vs gl5506

texts: What is the difference between gl5516 and gl5506? (in a SIMPLE way)


texts: How can I slow down a 240V AC motor used for an exhaust fan?

texts:
I've got a fan that is way too powerful and would like to find out how to slow it down.
Variable speed would be nice but I would be just as happy if I could say reduce it to a fixed speed i.e half speed.
It currently only has an on/off switch.
The specs on the fan are:

240 volt 50Hz 1500 watt
Single speed: 2900rpm

My ability level is enough to pull things apart and solder but I have no education in electronics.
Any insight into this would be great.

I'm just going to live with the fan as is and reduce air flow by other means to suit my needs.
Thanks everyone for educating me a little more about fans and electric motors.


texts: Why does adding a capacitor greatly improve this circuit?

texts:
I've been prototyping this pretty simple circuit for a while now:

simulate this circuit – Schematic created using CircuitLab

Description: C3 is charged to set point. Compatator out put goes high causing the MOSFETs to switch on the load. Switching load causes a voltage drop so positive feedback provides hysteresis. C3 must be charged in order to start the motor. Should input voltage be lost, motor will also continue to run off C3 until cut off point. I didn't include a link to the compatator because its data sheet has many models and is just confusing for people. The compatator has PUSH-PULL output with sufficient sourcing to drive M1.

I don't actually know what the specs on the motor are. It runs at 1.5V and 100mA isn't enough current to start it. Once running the 100mA input is sufficient to run the motor and keep C3 charged.

C2 was not part of my original design and the output from M2 was much lower than expected/desired. Messing around with the various R values didn't really have any impact. I intuitively felt the problem was with the MOSFETs. So I added C2 and that greatly improved the output characteristics.

Note that it works without C2. But there is a larger than desirable voltage drop over M2 without it.

However, I don't really know WHY adding it had that effect.

Can anyone shed some light on what the problem was and how adding that cap helped?

Update: This is only true when the power source is the bench supply. When the intended power source is connected (9V Solar), C2 causes the circuit to stop functioning. So I guess I will not be including it on the PCB layout, but I'm still pretty confused by this behavior.


texts:
for the below circuit I don't quite understand why the output voltage is negative.

In the book I read they say:
\$\ V_{out} = -K R_{L}V_{in}\$

So, why negative sign? Book says "The negative sign indicates
that the output is an “inverted” replica of the input circuit" - But why is it inverted? What caused this 180 deg phase shift?

Also, why they model transistor in such unintuitive way? I mean there is break in the circuit between V1 and I1, plus why the even introduce V1 if we have Vin which is aboiously eq to V1?


texts: MPPT charge controllers in series to handle high voltages

texts:
If I have 500v of solar power can I run 10 mppt charge controllers in series? So each mppt would only see 50v because I'd be using 10 cheap mppt controllers in series. From there it'd be charging a 24v system.
I don't think pwm would work well in this, but mppt might.


texts: Powerstrip's red indicator is flickering like crazy as long as no light is turned on in the room

texts:
I have a Belkin power strip with a red light indicator in it. I have used it for years and it functioned properly. Last night I noticed its red light flickering like crazy, i.e. constantly turning off for a fraction of a second and coming right back. Whenever I turn on any lamp in the room, the red light indicator lights up without fading or going away, just as it is supposed to, but as soon as I turn off all light in the room, the power strip's indicator starts flickering again. This happens when the power strip has nothing connected to it. Not sure if I should be concerned.

Does that mean I have "unstable current" in the socket or something like that and when I turn on the light the current starts flowing in room's wires and "stabilizes"?


texts: Would it be possible to make a USB Hub from scratch? Like, designing a PCB, and hand soldering components on to it? What microchip would I have to use as the controller? Is there a simple controller chip I could use for, say, a 4 port hub? I know I'm getting a bit hopeful here, but are there USB hub ICs in the DIP package?


texts:
I have the simple circuit as attached.

simulate this circuit – Schematic created using CircuitLab

The voltage V0 measured across the bridge rectifier BR1 is 9V, the voltage V1 measured across the resistor is 0.35V (the resistor is 16.8 ohms). The voltage V2 measured across the multiple LEDs is 8.65V.

By Ohms law isn't the total current through the circuit

I = V/R = 9V / 16.8  = 0.536A

If we use

I = (V0 - V1) / R = (9V - 0.35V) / 16.8 = 0.515A

or

I = (V0 - V2) / R = (9V - 8.65V) / 16.8 = 0.021A

But why is the ammeter reading a current of (A) 0A? (The multimeter has a resolution of 1mA.)

If the calculated current going through the circuit does not include the Voltage drop across the LEDs, why not, why is this voltage not used in the I=V/R calculation?


texts: Using a led driver as a led backlight inverter

texts:
Can i use a led driver to replace an led backlight inverter ?
I have an old MacBook display (LG LP154WP2) and don't really know how to use the inverter board, because i can`t identify the ic on the board.
Would it be possible to design a new board using a led driver ic like the LM43 line from TI or similar ?
Would there be any problems or are backlight inverters just cheaper led drivers for a specific application ?

Sidenote: Yes i know that there are whole solutions for interfacing laptop displays on ebay, this is more about the learning experience!


texts: Blow MSP430 security fuse with FET430 or MSP-FETFlash programmer

texts:
Is it possible to use a FET430, MSP-FETFlash or similar programmer to program and then blow the security fuse of the MSP430 devices?

We have 500 which already been soldered on the boards and were not programmed first.


texts: What is the type and name of this 15-pin connector pair?

texts:
This connector is suited on a Sony car stereo front panel. Searched the net however could not find anything. I love to extend the connection with a sort of cable so it possible to fit the front panel somewhere else.

What is the type of the connector?
What is the name of the connector?


texts:
I have question about an ESD protection circuit, as seen below, taken from a TI document;

My questions are about the additional zener diode on the right attached to the USB lines:
1. Is this for specific ESD protection on the USB lines?
2. If so, i've seen ESD circuits without this zener and just diodes, so what does this do and why is it needed?


texts:
Can somebody please describe the way that NMOS transistor layers:

DIFF
POLY1
NIMP
PIMP

are related to the cross section of it?


texts: How can I find maximum power transfer using Thevenin equivalent

texts:
As I understand it, should maximum power transfer be when $$ R_L=R_{th} $$ then $$ P_L= P_{L(max)} $$

So that this should do the trick:

$$ P_{L}=\frac{V_{th} ^2}{R_{th}} $$

But it seems that I am doing something wrong.


texts:
I am making a PCB using Eagle which features a few BNC connectors. Eagle comes with the RADIALL R141426161 component so I'll just use these instead of searching for other ones.

The component has the following schematic symbol and footprint

I see there are 5 pins on the footprint but only 2 on the schematic symbol. I assume one of the schematic pins corresponds to the central pin (signal?) on the footprint and the other to the 4 outer pins (ground?). Can someone clarify for me?


texts: Can we use 220V/60Hz Solenoid on 220V/50Hz supply?

texts:
Does anyone have experience of using 50Hz 220VAC for solenoid valve specified for 220VAC/60Hz ? It definetely will work, however is it safe/reliable in the long term?
The model of solenoid is ASCO 307 series, however I belive this question will apply to any solenoid/relay.

Thank you,


texts:
I am facing a strange issue while building a simple LED matrix. I am using the SK6812 LEDs and an ESP8266 controller. The LEDS will be controlled over Wifi. My matrix contains about 180 LEDs on a PCB of 25x25cm.

After about 120 flawlessly working LEDS there are strange lightning artefacts, like flickering and wrong LED color. All LEDs and the ESP are connected to the same ground. Also the logic shifter (3.3V to 5V) is working as it should. It converts the 3.3V data form the ESP to a 5V signal for the LEDs.

Additionally to the level shifting I added one 470 Ohms resistor (R2007) to the data line as suggested on this page.

Long story, short: If the 470 Ohms resistor is removed and the data line is bridged with a 0R Ohms resistor all LEDs are working flawlessly.

I am not much of an electronics experts, and asking myself what is the purpose of this resistor? Is it safe to remove it?
And, can this be the issue for my problem, or is it only a coincidence that removing it solved my problem?

EDIT:

The LED_DATA line is pretty long, as it travels over the whole board, front and back. My roughly length estimate would be around 13 meter. The track 0.25 mm thick and copper has a thickness of 1 Oz. Based on my calculations the resistance on the data line should be 27 Ohms.


texts:
I'm trying to program the ATSAMD21G18 on Adafruit Feather M0 and over SWD Using a Segger J-Link EDU Nano.

When I try to download the program to the chip through Atmel Studio it fails verification at address 0x000000.  This result is explained by the NVM Fuse field USER_WORD_0.NVMCRL_BOOTPROT, which is set to 2 protecting the first 8192 bytes in the flash. (I can verify this is actually the case by writing to individual bytes in flash, writing has no effect for addresses below 0x2000).

However, everything I have tried to change this memory has failed. Atmel studio reports a verification fail at the address of the Fuse (0x0804000). J-Link Commander doesn't report any error writing, but when I read back the value of the fuse has not changed.


texts:
I am currently designing a microgripper for which I need a proximity/distance sensor.

Please refer to the image below for design requirements.

Due to the force application (as shown in the image), the surfaces A and B undergo bending phenomenon. I need sensors to identify the distance between these surfaces during the bending process. I plan to use capacitive proximity sensor IC (as the material is plastic) either on surface A or both of them to create a capacitor like condition and measure the change in the distance between them.

The  dimensions surface are 18mm(length) and 4mm(height)

Could you suggest which proximity solution might work in this case? My idea is to use the two surfaces as capacitor plates but I need help in how to create a detection system.


texts: why is the reference of strain gauge changed depending on gains of amp? use ina128 and ad8542

texts:
I made a circuit for a load cell. It is available but when it is applied to the strain gauge, it has a problem.

Reference voltage : 1.65 V

When I measured value of load cell, I can see the change from reference voltage.

When measuring strain gauge,

measured Sig1+_input, Sig1+_input, Sig2+_input, Sig2+_input in schematic, and it is the value of about 1.65V, but when I changed some resistor for regulating gain of amplification, tge reference was changed as well as amplification of the change.

Primary amplifier(INA128) :

Gain of Rg = 1+(50k/Rg)

Secondary amplifier (configuring amplification circuit with AD8542) :

A = 1+(Ra/Rb)

For example:

When I put Rg=5.8k(10 times), Ra=40k and Rb=1k(41 times), I can see that the reference is 2.06V and the change is 200 mV, so the range of the change is 2.26 ~ 1.86 V.

When I put Rg=5.8k(10 times), Ra=80k and Rb=1k(81 times),
or Rg=2.7k(20 times), Ra=40k and Rb=1k(40 times)
I can measure that reference is 2.86V and the range is 3.26 ~ 2.46 V.

I wonder the why the reference increases and decreases depending on the resistors (Rg, Ra and Rb) changed.

If you know the answer, please let me know the cause.


texts:
Say a company has a parking garage for its employees, and they want to track the traffic in and out. So they require that all employees put some kind of tag in their car window, and they have some kind of reader at the entrance to the garage.

What would be the best technology to use in this situation (assuming cost is the largest factor)?

My initial thoughts were RFID tags because they seem to be incredibly cheap if you're only looking to measure over a distance of a couple meters. Are RFID readers that can read over a couple meters a viable solution?


texts:
The values for resistors in a typical series, like E12, follow an exponential series (hence the "E"?). 10, 12, 15, 18, 22, etc., everybody knows them by heart (at least E12). But often you want simple ratios in dividers, where a series like 10, 20, 30, 40, etc. would be more convenient. The problem with the exponential series is that, if 15/10 is the wrong ratio, so will 22/15 be, or 33/22. They'll all produce the same result.
Are there resistors with values 10, 20, 30,... ?


texts: How can the overvoltage prodection inhibit the voltage to let the voltage doesn't reach the destrutive level?

texts:
This is the voltage conditioning schematic,including OVP(overvoltage prodection) and LDO(low drop-out regulator),the OVP limits \$V_{buck}\$ to inhibit it reaching destrutive voltage level.

When \$V_{buck}\$ exceeds the limit voltage,the \$M_{OVP}\$ will be drived,and question is,"so"?i mean,i just turn on a MOS,how can it save something?

According to the explaination,the exceeding \$V_{buck}\$ must damage something,and it seems OVP rescue that "something",just like the fire burn the house,and the water  extinguish and save the house.

I know the fire is exceeding \$V_{buck}\$,and the water is OVP,but now,who is the house,LDO?


texts: Effect of switching spikes (400ns duration) on capacitor rated voltage

texts:
I have a motor drive which uses 63V electrolytic capacitors, which are the part with lowest-rated voltage on the drive's DC link. I measured the switching spikes on the DC link voltage (carefully, with spring-ground lead rather than ground clip to minimize lead length) and found on the order of 5V spikes at the 20kHz switching frequency with 48Vdc nominal; they last on the order of 400-500ns.

Here's my question: how do these switching spikes affect the 63V capacitor rating? Are they fast enough that I can ignore them and can allow the DC average voltage to get up to 63V? Or do I need to factor in these spikes, along with appropriate engineering margin, meaning I should stop somewhere in the 53-58V range depending on my conservativeness?

(Note: this assumes I am comfortable operating up to the low-frequency 63V rating, which I may or may not choose to do. That's a different question; I'm asking whether I need to take the high-frequency spikes into account.)

Cornell Dubilier's application guide states the following (subject to interpretation of course)

  Aluminum electrolytic capacitors can generally withstand
  extreme overvoltage transients of limited energy. Application of
  overvoltage more than about 50 V beyond the capacitor’s surge
  voltage rating causes high leakage current and a constant- Percent Rated Voltage voltage operating mode quite like the reverse conduction of
  a zener diode. The capacitor may fail short if the electrolyte
  cannot take the voltage stress, but even if it can, this operating
  mode cannot be maintained for long because hydrogen gas
  is produced by the capacitor, and the pressure build up will
  cause failure. However, special designs are available that use
  the overvoltage, zener-clamping efect to successfully protect
  equipment from overvoltage transients such as lightning strikes.

  Capacitors used as bus capacitors in large, high-voltage
  capacitor banks are less capable of withstanding overvoltage
  transients because the high energy and low source impedance
  of the capacitor bank can prevent a momentary partial discharge
  from self healing and cause it to become a runaway shortcircuit
  failure. For high-voltage capacitor-bank applications use
  capacitors proven for that use.

edit: The above voltage was measured across a terminal block (Phoenix-style) that connects directly to power planes; so does the capacitor. I have also measured directly across the capacitor itself at 24V --- had to tip up the board holding everything together by hand, press oscope lead and ground ring against capacitor terminals, so I'm being a bit cautious before trying this at 48V:

(Screenshots of Agilent MSOX3034A 350MHz using 500MHz 10:1 passive probe.)


texts: Advantage of using "IF Amplifier" over traditional OP amp?

texts:
I am trying to receive 1MHz ultrasonic signal with transducer.

So, I will need to design some kind of filter to only pass 1MHz signal and filter out other noise signals.

Searching online for OP amp configuration, I found something called "IF Amplifier".

Below is the link to datasheet.
[MC1350] - IF amplifier(Datasheet)

What is the advantage of using such specific IC over using generic OP amp with nice parameter(high input impedance and GBP, low offset voltage and output impedance)? In terms of noise performance, signal attenuation, jitter, and etc.


texts: Identification of camera component including probable metal composition

texts:
I realize this is probably off topic but am curious as to what electronic component might be shown in the following picture, and what metal it likely is made off. It is presumably part of the triggering mechanism atop a digital camera (Canon Powershot A1100 IS):

Note this is a follow up question from another SE site.

It would additionally be useful to know what conditions would most probably have led to formation of the salt that accumulated on the device. It is unclear what humidity it was stored under, or whether a battery was in the device, but obviously it was not properly stored. Could leaving an undischarged battery in the device lead to this type of salt formation?

Update: According to the original OP, the image shows part of the battery door. It is used to complete the circuit between the two AA batteries that the camera takes. Scraping away the blue crystal only results in more of what you can already see in the picture. Metal that looks grey in some places and brown/red in others


texts: Selection of wavelength for optical reflective sensing

texts:
Most of the reflective sensors in the market use either red or near IR wavelength and have a very short range (in the range of mm). Given the reflectance of the Si at different wavelengths and reflective material used for reflection, i need to select wavelength of the light for sensing long distance in dark environment(in the range of 10 - 20 cms). How does the distance between the sensor and the sensing object be taken as a factor in selection of wavelength?

As per my research, energy of light is based on intensity and wavelength. Intensity of light is inversely proportional to distance and the energy is inversely proportional to the wavelength.


texts:
I am looking for a AC mains voltage measurement circuit for my controller which has to be isolated. There are a lot of circuit using step down transformer, but all of them are too large for my project. Is there a possibility to use miniature SMT transformers, such as audio? Could they be used for isolation? After isolation I could rectify this voltage and use voltage divider.
UPDATE: The size of the transformer must not exceed 10x10x10mm. Transformer could be used for only isolation. The voltage I want to measure is 220VAC/50Hz.
Could this circuit do the job for the measurement? What about its safety and accuracy? https://microcontrollerslab.com/ac-voltage-measurement-using-microcontroller/
Thank you for your advices.


texts: I'm trying to find the distance between two bluetooth beacons which are typically in the distance of 60cm or less. Direction is not an issue, I'm only looking to figure out the distance between the beacons and there will be no interferences such as walls/objects in between. Is it possible to detect the distance through RSSI Measurements? and if so what will be the expected accuracy?


texts: Creating a circuit with 3 lights and 4 switches (1 master switch)

texts:
I'm a high-school junior in AP Physics 1. My class was assigned an optional, grade-boosting project where we could make a circuit under certain guidelines. I figured I'd give it a shot, but I'm really struggling at the design. Here are the guidelines:

You can only use wires, 4 switches, 3 lights, and one power source, and apparently now diodes
Switch 1 is a master switch, and must turn on all three lights while the other 3 switches are open
Switch 2, 3, & 4 must turn on an individual light while switch 1 remains open.

I have been using the Circuit Construction Kit from PhET found here, and I have really struggled. No other components are allowed. I eventually have to physically build the circuit and get the calculations of the current and voltages for each scenario, but I wanted to just get the design down. Any solutions or tips would be greatly appreciated!

EDIT:
Here is the original assignment page given. I am going to try to clarify with my professor about what components are allowed.

EDIT 2:
I have just talked with my teacher, and it seems that diodes are allowed, but NOT multi-way switches. He was very explicit about that.


texts: How to control a device that need to be updated over internet?

texts:
I know, the question is very vague, but I'll try to explain better.

I'm working in a school project and I got interested in continuing this project after school. It's a automatic aquarium. I want to control everything that happens in a aquarium, so I used an Arduino Uno connected to some sensors and some activators - sorry, I don´t know the right terms.

Everything works ok.

But... I got the idea to control this system remotely, connecting it to the internet through a wifi connection using an wifi shield. Ok, seems possible to do, but I also want to change all "program" remotely. I mean, the user, by a site or app, would be able to select a fish and the Arduino would change all the environment to better grow that specie. And I imagine it requires a "reprogramming" of Arduino and its seems impossible to be done by wifi connection.

So... The question is:

Can I achieve it using an Arduino? What version of Arduino? And How?
If its impossible to achieve it with an Arduino, how could I achieve it?


texts: Should one pour AC-Neutral copper on bottom layer when routing AC

texts:
I am designing a PCB where there will be AC mains routing/tracks.
What I want to know, is if it is better -for noise reduction- to take one of the AC outputs (Neutral) and pour it on the bottom side of the PCB (On the mains/AC side only of course), as I would do with GND if I was using DC.  (aka using Neutral and Phase routes/traces on different layers as much as possible)
So basically, treat Neutral as GND when considering tracing and copper pouring.
I think this makes sense since the one AC output is the return of the other and vice versa, but I have not seen any recommendations or questions about it while searching/googling, and I think that it might not even make a difference.
The closest to my question is this issue  But on the answer, @MadHatter says that

Yes it makes sense to put them on separate payers for better separation.

But I am not happy/satisfied with the "makes sense" reply.


texts:
What do I need to check for when assembling RJ45 cables. I had some left over CAT6 cable from when I wired my home, and I bought some CAT6 RJ45 connectors from a local store:

I cannot even push the individual color cable through the plastic guide:

So there is definitely something that is not compatible, or at least CAT6 is not enough to combine them. What should I look for on my cable spec to know for sure:

Which leads to:

NEX C6 450 F/UTP LSZH Dca 4P 500m IVOIRE


texts: Can I remove zobel network in LM386 circuit?

texts:
What happens if I omit this part?
Actually I don't have 10om resistor and I want to know is there any alternative?

ps: I know what is a zobel network. I want to know what happens if I omit it.


texts: How can I electronically sense the state of an LED in another device with an Arduino?

texts:
I'm working on a project to integrate an off the shelf garage door monitor with an Arduino. The base station has a pair of LED's that flash in different patterns to indicate the state of the remote sensor, and my thought is that I can read these by connecting them to the the input pins, however I have some hurdles to cross.  I've made some progress, but I'm just getting started with electronics and I'm unsure if I'm going in the right direction or if I'm going to fry $70 worth of stuff.

Here's what I know:

The base station has a 100mA 12V power supply.
The Arduino can use a up to a 12V power supply, but it's happier with 9V.
The voltage across the base station leads is about 1.9V when they're lit.
Arduinos use 5V logic, and read anything higher than 3V as high.

My plan is get a 12V power supply that can power both easily, feed the base station directly off of it, and use this converter to give the Arduino 9V. I assume that they share the same ground level.

Since the voltage across the LED is only 2V, which is not enough for the Arduino to read, I'm currently thinking of using a variation of this circuit below, which shows the ON state as about 1V and the OFF state as 5V at the input. The difference will be that I'll just run a wire from the positive side of one of the base station LED's to the transistor base.

simulate this circuit – Schematic created using CircuitLab

So, am I on the right track? Is there a better way to read these LED's using an Arduino?


texts: How to limit HV capacitor charging current?

texts:
I have a voltage doubler, which is connected to mains (without galvanic isolation):

It enticed me with its simplicity, configurability and option between charging speed or desulfatability.
The problem is that in real practice lamp eats 20-50% of wattage, what i want to avoid.

How could i modify scheme to get rid of lamp and raise its efficiency to 85-95%?

PS. It needs to be done by limiting current but not dissipating extra power in air as with lamp.

UPD. Nominals on upper scheme are wrong. here is scheme for one of simplier devices i have by hand, with exact soviet partnumbers:

UPD2. Before posting how inefficient and rude it is, and to understand what circuit do, and how low frequency high current SCRs works, you may use following working simulation, by tony EE and me:


texts: Voltage increase per cycle across capacitor for a boost converter

texts:
So I'm looking to make a high voltage capacitor charger using a boost converter and I'm wondering how much voltage the capacitor will increase per cycle of the boost converter. In reality, I would most likely design around a high powered inductor, charging to just below the maximum saturation current, then allowing enough time for the inductor to fully discharge into the capacitor (just on the brink of discontinuous operation).

I know that the discharge time will be dependent on the output voltage thanks to a previous answer. The voltage however will be changing with time as the current from the inductor decreases. The rate of decrease will also be dependent on this output voltage meaning for a fixed duty cycle and frequency, the output voltage will not rise linearly and the rate of increase will decrease as time increases.

How would I go about finding an equation for voltage increase per cycle? I'm assuming it will be likely iterative, depending on the output voltage of the last cycle.


texts: Can I use a multiplexer to connect a small capacitor to a 555 timer?

texts:
I'm making a circuit including a 555 timer controlled by an RC combination, where R is fixed and C is one of several capacitors (values around a few pF to a few hundred pF). I would like to connect the capacitors to the timer circuit using an analog-friendly multiplexer IC (like the 4051). This way, the 555 frequency can be set using any of the capacitors, depending on which is needed at the moment.

Would this actually work? Is this a correct use of a multiplexer chip? Does anyone have any recommendations on how to do this?

Edit: it needs to be controllable by a microcontroller, so a rotary switch won't work (at least rotary switches as I know them). Is there a better way--maybe a bunch of relays?


texts: Capacitive load at the output for analysis of CMOS cells

texts:
This question is very rudimentary one. Please point me to the link if this question has been already asked.

In general, when working with simulations and and analyzing the standard cells designed based on CMOS logic, a capacitive load is tied to the output of the cell or gate. Why is it not a resistive load but a capacitive one? The timing characteristics are measured after tying the output to a standard capacitive value. Wouldn't the delays measured during the simulations (e.g. using SPICE based tools) be affected due to the rise and fall times of the connected capacitor?

Edit: If the capacitive load seems a realistic option, wouldn't a RC combination be still simple and more realistic?


texts:
Problem background: My ultimate aim is to implement a SATA host controller on an Artix 7 FPGA. Having said that I am first focusing on the physical layer. Through my research I have found and read through open source IP located here: http://www.ecs.umass.edu/ece/tessier/rcg/virtex4-sata/sata_core.html

The IP described above is for an older family of FPGA devices and hence cannot be easily imported into the newer Vivado environment.

My question: Would it be better to start the physical layer from scratch using the 7-series transceiver wizard OR should I try to migrate bit by bit the old protocol to be used on the newer device?

Important notes:

Rocket IO transceivers are not supported in Vivado
The new device does not have a SATA output port itself like the ML405 board used for the open source core
From the product guide it seems like the 7-series transceiver wizard handles all the SATA physical layer things such as OOB, 8b/10b, comma detection etc. BUT there is no formal documentation or example design I can locate about SATA.


texts: Alkaline AA discharge curve at just a few mA (to replace a CR2032)?

texts:
I bought a pack of tealights each powered by a single CR2032 (flickering LED; builtin timer turns it on every evening for 5 h).  My wife loves them, but after just a fortnight each tealight's CR2032 has dropped to 2.2 V (under load), and the LED has become invisibly dim.  Discharge curves suggest that the mean load is 2.5 mA (which a CR2032 can maintain for 70 h, yielding 170 mAh).

Because I'd rather not replace several CR2032's per week, I'd like to replace the CR2032 with a pair of alkaline AA's.

AA's have roughly 10x the mAh, but in published discharge curves for AA's, the lowest testing current I found was forty times higher than my load.

Logging data for over a month would take unusual patience.  Has anyone done so?

To be precise: at a 2.5 mA load, how many hours will it take for an alkaline AA (of whatever brand name) to discharge down to 1.1 V?  (So a pair, down to 2.2 V, to emulate the CR2032.)


texts:
I am running a PIC24F32KA302 using the Low Power RC with Postscaler (FRCDIV) clock source at 250 KHz.  I would like to switch the clock in the code to 8 MHz FRC Oscillator with Postscaler and PLL module (FRCPLL).  I am using the CCS PIC-C compiler.  My code to perform clock switching:

void oscillator_16Mhz()
{
    disable_interrupts(GLOBAL);

    #asm
      MOV #0x742,W1        // OSCONH
      MOV #0x78,W2
      MOV #0x9A,W3
      MOV #0x01,WREG
      MOV.b W2,[W1]
      MOV.b W3,[W1]
      MOV.b WREG,OSCONH
      MOV #0x743,W1        // OSCONH
      MOV #0x46,W2
      MOV #0x57,W3
      MOV.b W2,[W1]
      MOV.b W3,[W1]
      BSET OSCON,#0
    #endasm

    delay_ms(200);

//  #use delay(internal=16MHz)   // For wifi Interface
    enable_interrupts(GLOBAL);
}

The dissasmbler listing:

98:                void oscillator_16Mhz()
99:
               {
100:                disable_interrupts(GLOBAL);
  0EC6  A9E081     bclr.b 0x0081,#7
  0EC8  200E04     mov.w #0xe0,0x0008
  0ECA  880214     mov.w 0x0008,0x0042
  0ECC  A8E081     bset.b 0x0081,#7

101:                #asm

102:                MOV #0x742,W1  //OSCONH
  0ECE  207421     mov.w #0x742,0x0002

103:                MOV #0x78,W2
  0ED0  200782     mov.w #0x78,0x0004

104:                MOV #0x9A,W3
  0ED2  2009A3     mov.w #0x9a,0x0006

105:                MOV #0x01,WREG
  0ED4  200010     mov.w #0x1,0x0000

106:                MOV.b W2,[W1]
  0ED6  784882     mov.b 0x0004,[0x0002]

107:                MOV.b W3,[W1]
  0ED8  784883     mov.b 0x0006,[0x0002]

108:                MOV.b WREG,OSCONH
  0EDA  B7E742     mov.b 0x0000,0x0742

109:                MOV #0x743,W1  //OSCONH
  0EDC  207431     mov.w #0x743,0x0002

110:                MOV #0x46,W2
  0EDE  200462     mov.w #0x46,0x0004

111:                MOV #0x57,W3
  0EE0  200573     mov.w #0x57,0x0006

112:                MOV.b W2,[W1]
  0EE2  784882     mov.b 0x0004,[0x0002]

113:                MOV.b W3,[W1]
  0EE4  784883     mov.b 0x0006,[0x0002]

114:                BSET OSCON,#0
  0EE6  A80742     bset.b 0x0742,#0

115:                #endasm

116:                delay_ms(200);
  0EE8  090BB6     repeat #2998
  0EEA  000000     nop

117:
118:               //   #use delay(internal=16MHz)//For wifi Interface

119:                enable_interrupts(GLOBAL);
  0EEC  A9E081     bclr.b 0x0081,#7
  0EEE  EF2042     clr.w 0x0042
  0EF0  A8E081     bset.b 0x0081,#7
  0EF2  060000     return

120:               }

I can set up the oscillator to run at the desired frequency in the code at the start of the program, and both frequencies work.  I am unable to switch between clocks.  The clock frequency does not change when I run this routine.

oIf anyone has any experience with clock switching on these parts, I certainly appreciate help


texts: How to visually determine the damping ratio when we know the peak amplitude

texts:
I am currently trying to understand this example from the book, where it visually calculates the dampening ratio given the peak amplitude as well as the natural frequency. Here is the graph from which a transfer function was obtained:

What they found out, is: "We estimate the natural frequency to be near the peak
frequency, or approximately 5 rad/s. From the figure above, we see a peak of about 6.5 dB,
which translates into a damping ratio of about 0.24"

How did they manage to get 0.24 by using the formula below? Is this a mistake in the book or am I not getting something?