texts: How to connect this amplifier to my symmetrical power supply?

texts:
I am relatively new to electronics.

I have this power supply. It is symmetrical because I need negative voltages to other parts of the circuit. The power supply input J3 receives 18 VDC. The 7806 and 7906 are working perfectly and the voltages measured there are 6.0V and -5.98V.

On another part of the circuit, I have this amplifier, using the IC TEA2025B. Because I am using a symmetric power supply that is derived from a VDC power supply, I am not sure what I should connect to V+, virtual GND or V-.

I have marked all points I don't know in blue, from 1 to 15 and at the end of this question I will show how I connected that.

First notice R1, R2, R5 and R6. I am using that to add a DC voltage to the audio, to shift it to the middle of the rail.

This is how I have connected it:

to virtual GND
to virtual GND
to +6V
to virtual GND
to virtual GND
to +6V
to -6V
to -6V
to -6V
to -6V
to -6V
to -6V
to -6V
to -6V
to virtual GND

But I am hearing an "helicopter sound", something like a feedback and as I increase the volume the pitch gets higher...

I have tried to connect these points differently but none works correctly.

How should I connect these 15 points? I think the problem comes from these 15 points incorrectly connected.

Unfortunately I do not have an oscilloscope, just a multimeter.

Thanks in advance.


texts: Why does this transistor limit the current so much?

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I have been trying to understand how a transistor works. I bought a simulator to be able to understand it better.
Below is a small circuit I designed. The load is a lamp. The characteristics of the lamp are 5 V, 50 W, so it should draw 10 A.
When I design the schematic without the transistor etc, it does draw 10 A.
However when I use the transistor weather I put on the lamp 50 W or 20 W etc it will not draw a "big" current.
Of course this is a "generic" transistor from the sim.
The sim gives me the following settings to configure the transistor (please check the bottom left of the picture)
I do not understand how to configure this transistor since those settings do not match with the datasheet information at all.

EDIT:
Without Resistor at all on the base Ib is too high but still Ic is "too low"


texts: Using positive voltage reference on a negative supply

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Got a 9V,0,-9V power supply and want to get two stabilised voltage references at 2.5V and -2.5V.

Is it possible to use a +2.5V reference chip "upside down" to supply the -2.5V?


texts: I am using an alu SN74ls181 . I am  unable to figure out how active high and active low are decided . Is it during the manufacturing or some circuit parameters decide if the circuit is active high or low.


texts: How can I see if my oscillator works without using an oscilloscope?

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I am an electronics engineering student and for my own experimental reasons I wanted to design a sine wave oscillator.
I actually want to create a home-made wave generator later on bringing all my little oscillators together and switching between them in time of need. I began with a Wien Bridge Oscillator for my sine wave generator.
I have really minimal practical and zero circuit design experience. After some simulations and tests I put together the circuit but I don't know if it really works or not because I don't have an oscilloscope. That's why I need an answer which doesn't involve one.
I tried bringing the frequency down to 1.5 Hz and attached an LED at the output of my circuit to see if there is any flicker. The LED is on constantly. On the other hand, the simulation works. Not a clean sine wave, not even close but at least it oscillates in the sim.
I put together a voltage divider to get three different outputs since I use a UA741CP op-amp. Later, I just attached a voltage regulator. I used 100k resistors to decrease the frequency. I will add both simulation schematic and my real circuit below.


texts: Is there a way to shield the fluidics of a solenoid valve from its magnetic field?

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Are there any solenoid valves on the market that specifically shield the fluidics from the magnetic field of the solenoid actuation? Either by physically redirecting the fluidics around the coils or maybe by shunting the field through mu-metal casing?

Also: If I were to transport ferromagnetic particles through a typical solenoid valve, is the magnetic field powerful enough (in a typical valve) to effect it, anyway? Should I even be concerned?


texts: Power supply protection to charge a battery

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I am using a power source to charge a battery. To protect the power supply from reverse polarity conection of battery I included a PMOSFET transistor like showed:

simulate this circuit – Schematic created using CircuitLab

The problem is that this only works when power supply if off.
If the power supply is on, so transistor conduces like VGS < Vt, and if now battery is connected with reverse polarity (VBAT < 0) there is a large current flow from source to battery like a short circuit, due to the large voltage diference between  V1 and VBAT, and the transistor still conduces.

Is there some way to avoid this problem?


texts: How do I protect a sensor IC from overvoltage when not in use?

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I am attempting to use an IC to monitor the value of an inductor in my circuit.  During normal operation a voltage higher than the maximum tolerated value will be present across the inductor.  There are intervals of time when the signal through the inductor will be turned off, and I would like to take inductance measurements during these times.

My question is this: How can I isolate the IC from the high voltages present when I am not actively measuring?  Would a BJT work for this, or potentially cause interference with my measurements in some way?  Is there a standard way to handle this sort of situation?


texts: Op amp gain calculations with resistor divider

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For the following schematics:

simulate this circuit – Schematic created using CircuitLab

Easy circuit - amplifies signal difference 10 times and offsets it 2.5 V.
The gain is said to be:

$$G = 1 + \frac{R_3}{R_2||R_1} = 1 + \frac{4530}{500} = 10.06$$

This is correct, I tested it in LTspice, but I don't understand one thing:

Why in the gain calculations we use \$R_2\$ and \$R_1\$ in parallel? I don't see how we end up thinking they are parallel, they have only one common point A, therefore they are serial to each other, why do we apply parallel calculations here?


texts: Finding the resistors value in a transistor circuit that uses a constant current source

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In this schematic \$ V_{BE(on)} = 0.7 V \$, \$ \beta=100 \$ and \$ R5, R4 \$  are unknown. After calculations I find that \$ R4 = 1.75kΩ \$ and \$ R5  =16.5kΩ \$ but I am not sure for these results. What is the right answer?

Can anyone help me if transistor \$ Q3, Q2 \$ act as a current mirror?


texts:
I'm trying to connect an old/possibly broken switch to a light from a 12V battery (very good first question isn't it?). The switch is meant to light Green when ON mode and Red in OFF mode.
The schema (as I traced it) looks like this but actually looks like shown at the bottom

My first question is, is the schema correct? I went several rounds tracing and came up with the same but it looks wrong i.e. when switch is ON there seems to be a short circuit but that obviously can't be right. So I believe the pins should be GROUND, +VE and CONTROL. But this doesn't align with what's printed on the circuit. So which one is correct?
My second question is, how can I wire this to a 4pin relay (to connect to a car battery)? e.g. something like this?


texts:
I am trying to evaluate a component (OpAmp) and built this simple circuit. I didn't use a breadboard due to high capacitance and noise, I just soldered stuff over the air thinking this would be low noise.

The bench power supply I have has about 80mV output noise, the LM317 is off the shelf and has high PSRR (60db). With 100mA load (simple resistor) I see 20mV noise at the LM317 output, when I connect the OpAmp it is still 20mV. The circuit is attached together with the photo of the proto.

Why the noise on the LM317 is very high? (I change the input voltage from 7 to 40, almost no change on the output noise,btw)

What else I could do to reduce this noise to a few mV?

Is it a good idea to build this simple circuit over the air? (i.e. would it be lower noise than proper PCB)


texts: Engineering approach to choosing a motor, voltage and gears

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I am working on a project to automate the opening and closing of my venetian blinds at home, by attaching a motor with an H-bridge to them. I started with a practical trial and error approach to it. For the motor I just got a small one I had spare, the kind you would use for an RC car, and for voltage I was connecting straight to different batteries and see what was the voltage needed to give enough power to the motor to open the blind. I didn't do any gearing to increment the torque.

After finding what I thought worked, I burnt a couple of motors, because (I think) I'm applying too much current to them.

I would like to use this opportunity to approach this project from an electrical engineering approach, the kind of thing you would do at university, where is more like a theory exercise to calculate your values in your design, and then apply it to the real world and fine tune the values to what's different from the ideal world of the theory.

I have a background in computer science and software engineering and it had a strong foundation on electronics and circuits, but nothing with motors.

I would love to know what kind of material, be it books/blogs/... would I need to study from the academic (maybe) electrical engineering world to not approach this problem blindly.


texts:
I would like to build a self-powered device on the surface of a vehicle without modifying it.
It is possible to generate enough power though thermoelectric generator by the temperature difference of the car surface (around 60~70 deg C) and street temperature?
What is the power output per unit area of a common thermoelectric generator in such a temperature gradient? Thanks a lots.


texts: 16X2 character LCD changes contract intermittently and doesn't work with raspberry pi

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I've been following adafruits RPi tutorials (and bought their starter kit)

I had an Sparkfun LCD Kit lying around. (It has an HD44780 controller LCD, a 10K trimpot and a 16 pin male header)

I soldered the header to the LCD, not all that well. I followed the tutorial step by step. This page has the wiring and I started bit by bit.

Symptoms : When I connected the trimpot and turned the knob a random bunch of boxes go dark and then they just  slowly lighten and disappear. Even when it happens is intermittent. Sometimes I turn the knob, nothing happens, sometimes it lights a few boxes and on their own they dim out.

Below is what is looks like.

This is the schematic of the whole connection. I doubled checked it a couple times. Nonetheless I ran the code the show stuff on the LCD and it just blinks a little randomly.

Is something wrong with the LCD? I messed the soldering?
Is there a possibility of my connections being wrong?
Could the trimpot be the wrong way in? (I tried both ways)

Could you help me narrow this down please?


texts:
For a design project at school I need a way to track a short distance underwater (swimming pool).
I have looked into programming an accelerometer to measure the distance traveled, but that is not accurate enough for the purpose I would like to use it for. IR and GPS are both not suitable to use for underwater purposes either because of accuracy and interference issues. I was thinking about ultrasonic waves but this seems to be an expensive solution. Any suggestion is welcome!

edit:
The aim of the project is help visually impaired/blind swimmers. I need to track the distance between them, while swimming, and the end of the swimming pool in order to advice them when to turn because this is a big trouble for them. So, How can I measure the distance between two points in the water, one moving and one stationary, in order to sent a signal when a certain distance is achieved?


texts:
I have a Bosch power drill, the same as in this other question.

I checked it carefully and it doesn't seem to have a capacitor or any other electronic components.

Does it mean the universal motor in it runs directly with the 240VAC?
Does it also mean that the rotational speed of the drill is 60Hz?
Can someone explain to me how that is possible? (I am new to electronics.)


texts:
Need your opinion in a design I'm working on. Please see circuit below.
So I need to control the mcu GPIO based on the incoming 24V signal. The signal is attached below. My issue is this 2 times out of 10 times, the mcu will not detect this signal. I tried adding 100n cap between 24V and GND, also tried increased 51k to 1M. But didn't make much difference.
Opto's minimum required current is 10mA.
Also, my second question, there is another channel in the 24V signal source, and when that switches sometimes my mcu detects that. Guessing thats due to noise. If you guys can suggest any improvements and get rid of incoming noise, it would be greatly appreciated.
Last two images are the noise.


texts: I am planning on testing a PoE evaluation board (https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/dc2093af.pdf) with a pwm motor circuit. The PoE evaluation board doc recommends putting it Vout through a dc/dc converter + PWRGD signal before supplying power to whatever device/circuit you are using. What would happen if I didn't do this and connected the Vout and GND to the pwm motor circuit?


texts: LCD screen gets hot and sucks power from Raspberry Pi

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Has anyone else experienced LCD screens overheating, and drawing too much current? I was trying a GPIO project with my Raspberry Pi in an attempt to interface with an LCD screen but for some reason my PI's OS shuts down while the black dots on the back quickly begins to boil (I'm guessing these black dots are heat sinks), and on top of that no characters display (thanks to my Pi being knocked out).

I know my pinouts are all correct as I used another LCD that worked great. I'm using two of the generic Hitachi HD44780s for this project, but they're from different kits.

Project tutorial I followed for both screens:

http://www.rpiblog.com/2012/11/interfacing-16x2-lcd-with-raspberry-pi.html

NOTE:
This happens when I connect my ribbon cable up to the Pi (the ribbon cable facilitates the wiring for the GPS), otherwise I can't start my Pi. What I've been doing is starting with my ribbon cable disconnected, boot up, and then I try plugging everything back into my Pi. Of course this just leads to the power being sucked up, crashing everything, and heating up the LCD. I'm also not powering the backlight, so that doesn't seem to be source of the problem.

Do I just have a broken LCD?


texts: Calculating current for a parallel array of in-series LEDs

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I am getting an odd reading from an array of LEDs, which I could do with a little help understanding. I have a very specific project, but to abstract this question from that, let’s assume the following:

I have 24 LEDs in 4 sets, each of 6 LEDs with a 68ohm resistor.  They are 1.8v LEDs using 20mA and I have a 12v supply.

simulate this circuit – Schematic created using CircuitLab

I understand how to calculate the required resistor and current for single LEDs but I used the rather excellent http://led.linear1.org/led.wiz to do the math for me on this.  It concludes my array will use 80mA.

However, when I use my meter, it tells me the array is only using 8mA?!

I am planning to run this from my Arduino Micro, which can easily deliver 8mA from a pin but certainly not 80mA, so the difference is crucial to me.

Initially I thought I was reading the meter wrong (it’s new) and I was out by a factor of 10 but the only other thing of a known(ish) current I could benchmark my meter with at 12v was the Arduino itself, which is drawing 37mA, which to me sounds about right (and 370mA would seem too high for a Micro), meaning my meter is probably correct?

I know you can get variations in LEDs or whatever, but I have 3 of these arrays and they are all reading the same ~8mA.  What am I missing or should this array be pulling only 8mA?  How should a parallel array of in-series LEDs be calculated?

Thanks for any help.


texts: How to make your own electroluminescent wire?

texts:
I saw Jeri Ellsworth's videos on making your own el wire.  It looks simple and since I do neon work, I have a collection of many different colored phosphors.

I tried two ways to make the wire: sticking the phosphors with E6000 glue, then using a paste made of soda (a sneaky neon tube bender secret!) and neither method did anything.

I'm suspecting that the glue or binder or something else in the phosphors is the key.  I suspect it's somehow conductive.

Has anyone made their own el-wire or el-display -- by making their own phosphor inks?


texts:
I want to make a simple box with one button. Pressing the button will send a SMS Text message to a preprogrammed phone number.

I have not designed a phone hardware before so looking for some simple reference designs to do this, looking for a starting point really.

So, a reference design to start the work would be helpful - thank you.


texts: How to generate a short (µs) high power pulse

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I'm faced with the following problem. I would like to send a current pulse of about one amp through tissue with a resistance of about 3000 ohm (so I need 3000 V obviously).
The pulse should be as short as possible (I'd say no longer than 10 µs). The shape of the pulse is not that important, but it should be reproducible and short and deliver about 30 mJ or more.

And the whole thing should be as cheap as possible.
So far I've collected the following ideas:

Building a mini Marx Generator:
Kind of like this http://www.electricstuff.co.uk/marxgen.htm
Maybe triggered by a relay.
As i understand it the unloading time decreases with the capacity, so two charged capacitors connected in series would halve the unloading time, so one could work with this (according to my estimates) but I'm not really sure about the reproducability and I have little experience in electronics anyway.

Another idea would be to use a flashlight used in photography, here I'm not sure if the pulse would be short enough. Or a high voltage switch.

I'd be grateful for any ideas thoughts and suggestions.


texts:
I'm trying to find the part numbers for FETs used in a 4in1 quadcopter ESC.

ESC information (as advertised):

brand/model: HAKRC/HK1S
voltage 1-2S Lipo or 1-2S HV Lipo, which translates to roughly 3.3 - 8.7 V
current: 10 A continuous, 12 A for 5 seconds
firmware: BLHeli_S O_L_05

The firmware variant ("O") points towards a pair of P- and NFETs for each phase, but that's not 100% sure.

Microscope pictures:

There are three chips marked "SP1 645" and three chips marked "AKW 3FAB" per phase.

Doubts have come up regarding the max voltage rating, because the MCU might not be able to pull a PFET's gate high enough to fully switch it off. FETs were reported to blow up when a 2S LiPo is connected. This seems plausible because there is no additional circuitry present to drive the high side FET's gate, unless the chips aren't ordinary FETs.

EDIT:

I was able to trace some signals and here are my findings.

The chip labeled "SP1 645" in the first picture has direct connections to

Bat+
a motor phase output and
the EFM8BB1's pin 8, which is P1.5. In BLHeli_S terms that's "Cc", or "phase C com FET gate output".
-> it's probably a PFET.

The chip labeled "AKW 3FAB" in the third picture, next to the black lead has direct connections to

Bat- (or Gnd),
the same motor phase output as the chip described above
the EFM8BB1's pin 9, which is P1.4. That's "Cp" or "phase C PWM gate output" in BLHeli_S.
-> it's probably an NFET.

The EFM8BB1 is directly powered from Bat+. The absolute maximum for this chip is 4.2 V, which is pretty much exactly a fully charged LiPo. The SOT-23-6 part is apparently a boost regulator because

it sits opposite to a large inductor labeled "100" and a diode labeled "K34"
the ESC has 5 V output on a pin labeled "5V" even if it is only supplied with a lower voltage through Bat+

The connections found so far support the impression that this ESC can't handle anything above 4.2 V. The FETs might be able to, but the whole ESC can't.


texts: How to Design method to Program & Calibrate a Panel of PCBs

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I'm designing a sensor-package PCB which needs to be programmed and calibrated while still in a panel of 10.
I'd like to avoid a large bed-of-nails type setup for this step so that the panel can easily be fit into a calibration chamber and not be obstructed.
My first guess is to route some signals from each PCB onto the panel to some sort of edge connector. But from what I've read: some people try to avoid this due to risks of shorts and traces being ripped up when de-panelizing.
Have you solved a similar problem? If so, how? Are there any other options which I'm not considering?


texts: Waveguides: How can you propagate at only one frequency?

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In a rectangular waveguide, we know we can find cut off frequency as a function of mode and geometry.

Is there a way to design the waveguide so to ensure that we can limit the frequency of transmission to a single frequency?

If not, can we design the waveguide so that the frequency capable of being propagated is between $$f_a < f < f_b$$

Thanks


texts: Component that activates a switch when charged?

texts:
this might be super basic but for a geologist it is killing me. I need a low voltage AC device (specifically a dog training collar) to wire to a flashlight so when the remote is pressed the light turns on.

Would a relay (SPST) do this or a MOSFET or??

I have 2 wires off the terminals on the shock collar that output 2V AC at about 2000 uA.

The flashlight has a lead off the batteries to a manual switch. This component needs to replace that manual switch. I am pretty sure every action movie out there uses this scenario .. Lol


texts: Getting 3.6V, 1.8V, and 1.1V from 12V using LM117 or LM317

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Please all, I need some help in designing power lines for my project.
I intend to use one LM117 (or LM317) to have at least three voltage lines on my breadboard, i.e 3.6V, 1.8V and 1.1V from a 12V supply (all DC).

I used the following formula to try and get a 1.1V DC line.

$$ R_2=R_1 \left( \frac{V}{1.25}-1 \right) $$

The tutorial I read suggested a standard value for R1 to be 240 ohms, which leaves me with a negative value for R2 (and for some reason i think this is wrong), for example:

$$ \begin{align}
  R_2 &= 240 \left( \frac{1.1}{1.25} - 1 \right)\\
  R_2 &= -28.8
\end{align}$$

Any ideas where I am going wrong? Should I be using a different value for R1?
For a background, I am trying to have three power lines of 3.6V, 1.8V and 1.1V from a 12V source (all DC) using the LM117/337
Can I have all three power lines off one LM117/317


texts: Raspberry Pi- SPI with Hi-Res Bipolar ADC Chip (LTC1867). Wrong values being read

texts:
this is a follow up to my previous question "How to measure bipolar analog signal accurately (to 1mV) on raspberry pi" . I can't post more than 2 links yet but please have a look for some more background. The summary is that I need to measure a bipolar signal that varies between +/- 2V. I need the values to be accurate to about 1mV. After, asking here, I proceeded with what I thought was the best way which was to use the LTC1867 chip which is a 16 bit ADC that takes bipolar inputs to eliminate errors from level shifting circuits.

I tried to use the guides for connecting the MCP3008 to connect the IC to the raspberry pi. My connections were SCLK->SCK (Purple), MISO->SDO(Green), MOSI->SDI(Yellow), CE0->CS/CONV(Blue).

I used spidev for the SPI communication, because it looked like the most popular one (I didnt quite understand WiringPi). I tried to get a differential input between channel 0 and 1

From the datasheet the input word would be 0000000X. And since it returns 16 bits I assumed I needed to send 2 8bit words. So I used spi.xfer2([0,0]). It returns 2 words. I shift the fist word by 8 bits and combine them both into one word. Since in bipolar mode, it returns it as 2's complement, I convert it to a normal number. However the answer I get is way off. So my questions are

Have I connected the ADC to the raspberry Pi correctly.
Am I sending and receiving the bits correctly?
How do I use Wiring Pi to communicate to the ADC or how do I communicate with ADCs that aren't MCP3008 and similar.
Lastly, while checking he SCLK signal on an oscilloscope, it showed no pulses. Any idea why?

PS: I can post my code as well but didn't want the question to be too long


texts:
We are working on an LED dimmer circuit which supports DALI2.0 Interface. We already received the hardware and working on software only. LED driver circuit is based TPS92515HV and below is the circuitry

But the issue is LED flickers when dimming below 3%. There is no Voltage-Current stability below 3%. Is it a problem with analog dimming. Hardware designers went to analog dimming decision after experimenting on both analog and PWM dimming and found PWM more prone to flickering. I'm not sure whether they have tried shunt FET dimming. What is the actual reason behind this issue and how to get rid of this?


texts: Display Driver for a SHARP LS020B1DD01D LCD

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I am working on a personal project that will feature an LCD panel and push buttons to control the graphical user interface. For the LCD I would like to use the SHARP LS020B1DD01D (for the specifications, see http://www.panelook.com/LS020B1DD01D_SHARP_2.0_LCM_parameter_20847.html) due to the size dimensions and resolution. I have been researching for several days, trying to find a compatible display driver for it, but as I am not very experienced with using separate LCD's and display drivers yet (up until now, I have been using display modules that already include the driver board), I am having trouble finding the right part for the job.

Are there certain key specifications that I should be looking for? How does one usually go about choosing the best display driver for their embedded system projects? Are there any online resources that could be helpful for finding a solution or learning more about this subject matter?

Note: Like I said, I don't have much experience with this, so please forgive me. I appreciate any feedback you can provide.


texts: How to use LFSR to generate random numbers as per this Xilinx application note?

texts:
The Xilinx App note XAPP052 "Efficient Shift Registers, LFSR Counters, and Long Pseudo-Random Sequence Generators" shows a method on how to use LFSRs to get random bit sequence of maximum length. I expected this to be a chain of registers similar to one used for CRC checks where we use feedback XOR gates to generate the random bit sequence. However, this appears different.
There are few things that I am trying to understand here:

How are they implementing a 32-bit LFSR using 2 16x1 SRAMs and 4 DFFs? Shouldn't it be 32 DFFs with some taps using feedback? The inclusion of Synchronous RAM blocks is confusing.
What would be the structure to implement 12 bit and 16 bit random bit sequence?
In Table 3 it gives the "XNOR form" and the length of the chain used to generate the random bit sequence. Is there a way that I might carry out simulation using this information in C language or otherwise?

The mixture of DFFs and Synchronous RAM blocks is confusing me as it does not match a simple shift register chain with XOR gates in feedback as used with CRC checking hardware. The reason I expect this to match CRC hardware is that both have concept of a polynomial that decides where we tap to get the feedback bits.
Edit:
I would be grateful if someone can clarify the relationship between Tables 1 & 2 and the Table 3. Why are there only 4 DFFs each time and they are providing address into some RAM blocks? That is now how shift registers work.


texts:
I am currently using a 5V DC, 1 amp wall wart to  my circuit which is on a PCB.  The wall wart plugs into the PCB using a barrel  jack.  All in all, my circuit uses around 300mA and can take between 3.3 and 5V.

However, I am really not a fan of the wall wart.  I thought about trying to "hide" it in the enclosure but it doesn't fit well.  So I have been looking into alternatives.

I came across the LNK304, LNK305, and LNK306, an "efficient off-line switcher IC that can support , -boost and flyback topologies".  It looks promising to me.  Specifically, on page 4 of the datasheet there is this picture.

My question is, is this a viable replacement for my wall wart?  Is there a better option?  What else would I need to get this to 5V, 300mA?  Would it be Ok to add the circuit to my PCB (with proper spacing for tracks on the board)?  Should I put this in a metal case connected to ground or a plastic case?  Is there anything else I should know that would help in making this transition?

If you need more information, let me know.  Any information on this would be great.  Thanks.


texts:
I've designed simple power supply with LM2576-ADJ for 12 V input and 5.35 V output at 3.0 A load.

Problems:

1- Output voltage changes rapidly and peak to peak is around 950 mV.

2- Output voltage drop to 4.10 V with 4 ohm load.

Schematic:

PCB:

Peak to peak with minimum load: 941 mV

Peak to peak with 4 ohm load: 620 mV

Pin2 output minimum load:

Pin2 output 70 ohm load:

Pin2 output 4 ohm load:

Output minimum load:

Output 4 ohm load:


texts: Connecting BeagleBone Black using serial port - voltage

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I want to connect PC to BeagleBone Black using serial port. There is a note on the BeagleBone website that I need a 3.3 serial adapter.
I do have a converter USB-rs232 using FT232RL, that gives me at the output 5v (I think so).

Can I make a voltage divider for output of my converter to make it 3.3V or do I need another converter 5V-3.3V?

EDIT:
This converter produces 0-5V voltages, I was using it earlier for communication with Atmega16 and it worked fine.


texts: How do you identify what capacitor to use to filter DC voltage ripples from a bridge rectifier? (capacitance, etc.)

texts: Let's say I have reduced 220V 60Hz AC to 1.5V 750mA AC with a step-down transformer and used a bridge rectifier consisting of 4 IN4007 diodes to convert it to DC. How do I math this down?


texts: Why IC 4081 is taking 2-5 seconds to set the output to low

texts:
Why IC 4081 is taking seconds to set the ouput(11) to low whenever I detach either input (I'm using a breadboard so I'm just detaching cables, I still haven't figured out an good way to use a switch with that kind of board)?

Battery 6V (+.21)
R1 = 1KOhms
A simple LED
Average Current = .3mA

I'm bad at drawing =/ and gEDA represents the IC as a gate.


texts: What do ripples in frequency response curve of filters depict?

texts:
I am trying to understand the frequency response curve of various types of filters (Butterworth, Chebyshev etc).

The curves are shown here for reference :

One thing I do not understand is what do the ripples in passband show.

The curve is clearly Gain vs Frequency. So all the ripples show is that the gain of filter varies slightly with the frequencies in the passband. How is that suppose to create a problem ? We will only get an output which is varying in amplitude. It would have created a problem had we been getting a distorted output, which was possible only when the filters introduced a distortion, and I dont think it has anything to do with gain at different frequencies.

Based on above assumption, why would one not simply opt for a filter with steepest rolloff (elliptic in the figure) , without worrying about the ripples in passband ?

Edit :

It seems I am not able to properly express my doubt. Here is another attempt :

Many articles on filter design mention "Butterworth response is maximally flat, while others like Chebyshev and elliptic have ripples". My query is what has this "maximally flatness " or presence / absence of ripples anything to do (if at all) with the purity of applied signal. Purity in the sense, I apply a signal of a particular frequency, and I get an exact replica back. Will the situation be different in case of different filter types, ie , will I get some spread out or mis-shaped waveform if the filter response has ripples?

If that is the case, then how can this be inferred from the frequency response curve alone , because frequency response curves only show that the gain of the filter varies with frequency ; they dont speak anything about what the shape of wave will become if the curve has ripples or not.

My doubt arises because the texts generally differentiate between various filter responses by citing something like "Chebyshev response differs from butterworth because it has ripples in the passband".

Additionally, if all of the above is not true, ie ripples bear no relation to altering the shape of input, then what do they signify ? ( One of the users made and attempt at that. If possible, please extend or elaborate a little)

I am talking of only a simple situation with just one input (let alone many inputs). Maybe someone is kind enough to point me to some resources which show response of these filters to a single sine input.

Thank You


texts:
An embedded device based on ARM926EJ-S revision 5 (ARMv5TEJ) chip.
The PCB have 8-pin test points for connecting JTAG debug interface (2.54mm pitch).
I tried to find specification for this type of ARM JTAG header and interface pinout table, but can't find anything. I find some description of another device that based on same CPU, but its not too helpful.
Can anyone help to define a pinout for this type of JTAG connector? Or any specific implementation may not follow JTAG standard format?


texts:
I am really stumped at this:

I've been mulling this over my head for literal hours. I am pretty sure there should be 4 currents, because there are at least nodes with 3 parallel resistors. I just have a really hard time reading why the currents are placed the way they are in a very awkward manner. I really think there should be an I4 at the third loop, but it may not be relevant to the questions... I'm not sure. Just to keep anyone from answering my HW questions, I blocked them out, for decency's sake.

I just really need help understanding why the currents are placed the way they are. Is it true there are only 3 currents? This setup makes it very hard for me to use KCL or KVL. Should I use KCL/KVL, or is there another way? I have figured out I1 using equivalent resistance, but now I'm stuck. One of the questions asks me to figure out I1, I2 and I3 using a source voltage, but how when I4 is missing?? I just don't know how to figure it out.

Please help.


texts:
I'd like to know how a USB to serial adapter (such as the FTDI FT232RL chip) works.

The way I think it does is the following:

Picture a system composed of a MCU, a USB to serial adapter and the PC host.
The MCU communicates with the serial adapter using a serial protocol (such as TTL) through the UART interfaces of both the MCU and the adapter.
The UART data is then translated to the USB interface on the chip by its internal hardware (and firmware since I'm assuming there is a MCU in these modules).

The USB interface (which is a CMC-AMS class) is identified by the PC and it loads the appropriate drives. What these CMC-AMS drivers do is create a virtual serial port, meaning the PC application communicates using a serial protocol and the driver makes the translation into the USB protocol for the communication between the USB interfaces of the PC and the adapter.

This is what I mean graphically:

Am I close to the actual answer?


texts:
I know that wire wrapping was used in critical applications where reliability was a major concern because it is more reliable than PCB based assemblies. But is it still true?

The AGC (Apollo Guidance Computer) was wire wrapped but what about current designs?
Are mars rovers, space telescope or critical nuclear power plants systems wire wrapped?


texts: USB-C UFP CC configuration: What Rd resistor value i need to use to be able to draw up to 3A?

texts:
Basically I want to add usb-c ports to my projects so i can use them to draw power.

From what i understand i need to put 2 5.1kOhm resistors between CC1/CC2 and ground. Would this allow the consumer device to pull up to 3A from the host, or would be limited?


texts: Program ESP32-CAM via FTDI without manual reset?

texts:
When programming the ESP32-CAM with an FTDI, I proceed as follows:

Connect GPIO0 to GND.
Reset the ESP32-CAM. (by cutting power)
Run:

python2 $(which idf.py) -p /dev/ttyUSB0 flash --baud 2000000

Afterwards, to monitor output:

Remove GPIO0 from GND.
Reset the ESP32-CAM. (as above)
Run:

python2 $(which idf.py) -p /dev/ttyUSB0 monitor

Is there a way to do all that without touching any cables or buttons?

Further information:

I reset by cutting power because the reset button is inaccessible with the ESP32-CAM on a breadboard.
I was hoping that the CTS or DTR pins on the FTDI could somehow be used. The ESP32-CAM will not be powered from the FTDI. It will be powered from an Adafruit 1000c booster, which has an enable pin.


texts: Delay relay triggered by switch turning off

texts:
I've got a dilemma. I'm trying to set up a delay relay for a boat shower waste pump.

The waste pump is triggered by some microswitches when water flows to the shower. I want the pump to continue to run once the switch has been disengaged (shower turned off).

At the moment, my relay setup activates when trigger switch is turned on but disengaged after x seconds (potentially whilst still in the shower!). I want it to continue to activate whilst the trigger switch is on and delay once trigger switch has been turned off. What should I be looking for?

Ps.I can't find the answer to my question in the forum


texts:
I have been researching various ways to control DC fans and out of curiosity bought a fan that has a 4-position switch with off, low, medium, and high settings. I thought that a voltage divider should not be used as a power supply.

I drew the schematic for it (2 surface mount resistors and 4 position switch) that includes my measured voltages.  I think that it is putting 1.87V across R1 (0.27W) at the low setting and 1.13V across R2 (0.21W) at the medium setting.  I left it running for hours and there was no obvious heat build-up.  How did they get away with this?  The ground plane and solder pads are pretty big, could that account for its performance?


texts:
I am trying to derive the expression in the question, to not much avail unfortunately. Here's what I did, using the hint:

\$v_{i1}-v_{id}/2-v_{id}R_2/R_1=i_GR_G+v_{i2}-v_{id}/2-v_{id}R_2/2R_1\$

\$v_{i2}-v_{id}/2-v_{id}R_2/R_1-v_o=(v_{id}/2R_1-i_G)R_2\$

These yielded,

\$i_GR_G=-v_{id},v_o=v_{i1}-v_{id}[1+2R_2/R_1+2R_2]/2\$

Which got me nowhere. Moreover, if

\$v_{i1}-v_{id}/2=v_{i2}-v_{id}/2\$

Then why isn't \$v_{id}=0\$??


texts: KiCad generating blank PCB when building from schematic

texts:
I'm relatively new to KiCad, but I've had some success in the past generating boards and having them manufactured - though admittedly it's been a while.
I'm using 5.1.9 on MacOS 10.14, and I've generated my schematic (just a simple 3x3 switch matrix, plus an extra switch) using just two different components:

11x switches using an imported symbol/footprint (from SnapEDA) of an Omron B3F-4055 pushbutton switch
1x 1x8 2.54mm pitch connector (for which there wasn't a footprint, but I assigned one)

When I initially generated the netlist from Eeschema, Pcbnew opened to an empty window. I don't mean a blank board, I mean a window with all the editor chrome and options, but no board to edit.

If I randomly click around in the empty window, I can seemingly select parts that are invisible to me, so I think it's there, but I can't see it for some reason. (Note the different details on the bottom of the window)

Searching around, I found a similar post here that said to use the Update PCB From Schematic tool. I used the tool, learned that the connector (J1 on the schematic) didn't have a footprint, and assigned a similar footprint that will work for my situation using the Assign Footprints tool in Eeschema.
Now Update PCB From Schematic passes just fine - no warnings or anything - but I still get an empty PCB file. So I'm kind of at a loss here.
Hopefully that's enough info and it's something stupid I'm doing. I attached a few images to show what I made and what I see.
Thanks in advance!


texts:
I have a large circuit involving feedback as follows

I am trying to find the closed-loop gain of this. Before I can do that, I need to find the open-loop gain. Thus, removing the feedback loop, M2 becomes useless and I am left with a common-gate stage below

Now, I need to find the gain of this circuit Vout/Iin and I make the following small-signal model

I can't seem to get Vout/Iin from this. Any ideas?


texts: What's the simplest (smallest) way to dim a DC LED strip with a switch?

texts:
I apologize for asking about what is probably the most simple problem to you folks but it seems I am ignorant of all the basics of electronics and Google did not help me here.

This is a 12v DC system.

When I say 'switch' I mean I want 'high beams' and 'low beams' effectively.   High being the full amount of current that the strip wants and low being 1/2 or 1/4 of what it wants. I've attached pics of the specs for one strip that claims to be dimmable.  I do not need exact specified amounts of current. My purpose is simply reduced light output and reduced energy consumption at the flip of a switch.  But I do want it to be efficient in that it doesnt just 'burn off' the excess current as heat.

Is there a simple way to do this?

Thank you.


texts: Why does my UART connection still work without connecting ground?

texts: On my prototype PCB, I have a microcontroller with reserved pins for UART communication with a debug terminal. I'm curious from a theory perspective about why my terminal works fine whether or not I connect ground to my USB UART adapter. I come from a computer science background, so assume my EE fundamentals are lacking.


texts: How to neatly solder the following TRRS connector?

texts:
I would like to solder the following TRRS connector, which seems to be more difficult than the usual TRS connectors:

I already know the order of the connections (TRRS = left, right, gnd, mic), what I would like to know is how to make the solder neat.

I tried putting the wires coming off to the side and it was messy and took a while to get it right such that the cover would fit back on. What is the correct way to tackle this solder job? Should I be guiding the connections sideways or straight? Do I need a smaller soldering iron because I am melting the plastic?

The idea of using magnet wire to make the connection has been offered, but I am not clear on how to do this in a way that will not interfere with the casing of the connector.

EDIT:

I have found a video that deals with soldering this connection, albeit for small headphone wires. The technique used is to put a drop of solder on each contact before pressing in the tinned wires (still quite tedious). I suppose this means that the connection was designed for smaller wires and I will have to either splice to a different cable together (yuck) or look for a different component.

I am still interested for any answers which would allow the pictured cable and TRRS to join together neatly.


texts:
I ordered a set of optocouplers the other day and was excited when they finally came in. Unfortunately, I've having a bit of trouble getting them to work. Simple on/off tasks work fine but when I attempt to use it to send MIDI data to an Arduino Uno I get no response. I suspect that the problem lies in the type of optocoupler I'm using. While the majority of projects on the internet seem to use the 6N138 I figured I could swap it out with the similar 6N38. Currently, I think the problem is switching time. The 6N138 is a diode optocoupler while my 4N38 is a transistor optocoupler. But without an oscilloscope I have no easy way to be sure. To complicate things, I can't find much in the way of any circuit using the 4N38 despite it's similarity to other chips. Is it possible to transmit MIDI data with this chip? Should I just buy a different one?

NOTE: VCC is 5V.

EDIT: Corrected part number.
EDIT: Specificity.
EDIT: Added schematic.


texts: USB Connector not following USB Protocol

texts:
I am developing a product that will communicate with each other via a cable and would like to use USB micro-B type connectors. However, the communication protocol will NOT be USB compliant. Is there a rule against creating such a product? I am planning to keep the power pins the same as standard USB so it can still be charged via a standard USB port or charger, but the data pins will use a proprietary protocol that cannot communicate with standard USB.

Thanks in advance,
Jason


texts: A question about replacing voltage outputs with 4-20mA current outputs

texts:
Some transducers have both voltage and current output options.
I currently use voltage outputs with around 15m BNC cables single-ended. So they are open to interference as well. Sometimes during data logging I observe noise.

Would using current output/loop in this case reduce the interference picked up along the way from the transducer to the receiver/adc?


texts: Should gold tips be on the top and bottom copper layers for PCIe golden finger?

texts:
I am trying to order a PCIe golden finger. It is my first time to create this type of PCB. May I just double check that

Gold tips should be on the top and bottom copper layers, right?
I should do hard gold plating, right?
Is it necessary to have beveling?
I asked OSH PARK before since they dont provide beveling, they told me it doesn't matter. Since OSH PARK cannot do 4-layer work, I changed to Royal circuit, which can do beveling. I am not sure whether I should have it or not as Royal circuit also says that they can process standard ENIG with no bevel.

Thanks so much for your help!


texts:
I have a question regarding the MOC30XX series opto-couplers. What is the real difference in their operation? So far I know only that the forward current of the input driving diode is 15, 10 and 5 mA respectively.
Is there any difference in their theory of operation, ie. auto turn-off at 0 cross etc? I would appreciate all info.


texts:
I would really appreciate if someone could give me advice on how to build circuit for this case. On my circuit input I have slowly arising voltage from 0V to 10V, and on my circuit I have 2 outputs. When input has 0V-5V, first output has to be active, but when voltage rises from 5V-10V, first output has to deactivate and second output become active. And vice versa, when voltage decreasing to less than 5V, second output has to deactivate and first become active.
5V is the point where output changes, depending on voltage.
I was thinking to use 5V or 6V relay which gets active when voltage gets close to 5V. But relay coil will always use energy, which is not good in my case, as I need as much as possible voltage and current on outputs. Can you help to project switching between two outputs using transistors or comparators circuit? Thanks in advance.


texts: How does this resistive pull up and resisitive pull down circuit work?

texts:
In PSoC Creator, there is a resistive pull up and resistive pull down. From the documentation, the initial drive of pull up is logic 1 when for pull down is logic 0.
Pull Up:
When the  DR=1, the upside transistor will switch on, whereas the downside will switch off. Then, what happens in the buffer?
Pull Down:
When the DR=0, the upside transistor will switch off, whereas the downside will switch on. Then, what happens in the buffer?
Actually, what is the effect of the pin that is connected to the buffer?


texts: Changing pad shape/size selectively on an inner layer in Eagle

texts:
I'm trying to create a plated cutout in eagle for a DC barrel jack connector (https://www.sparkfun.com/datasheets/Prototyping/Barrel-Connector-PJ-202A.pdf) for a 4 layer board to be fabed by oshpark.  I've followed the general guidelines provided by eagle:

In the package I used a long pad with a drill size equal to the shortest dimension of the desired rectangle.  I then drew a rectangle of the desired cut out on the middle layers and milling layer.

The trouble is that oshpark doesn't use the milling layer -- they want all holes on the dimension layer so I am forced to copy the rectangle onto the dimension layer too.  The DRC for oshpark also dictates a 15 mil spacing between copper and dimension.  What this means is that I'm left with a pad that's unconnected on the inner layers because the dimension layer +15 mil spacing is too far away from the pad on the inner layer.

Obviously it would be nice to have that connected.  I played with the restring of pads and can of course increase that so there's contact as shown here:

The problem is that now every pad now has this property, which isn't desirable.  Is there anyway to either change the shape of inner layer pads selectively or selectively change the restring value for a package?  Alternatively is there anyway to accomplish what I'm trying to do in another way?


texts: Can I run a 110v battery charger/maintainer off a solar panel?

texts: I have a Batt Cat II battery charger/maintainer hooked up to the batteries on my boat. I keep it at a storage yard that doesn't have 110v outlets available. I was wondering if it is possible or practical to set up a solar panel that could feed the charger/maintainer. I'm not the most knowledgeable about electrical systems but I assume all I would need is a panel, controller, and inverter. My biggest question is what would be the minimum wattage needed to supply the charger. I have no idea what the pull is when the charger is running but I know most chargers pull 1 or 2 amps while charging. Any insight would be very helpful.


texts: Where can I get knowledge on transient mode boost converter for SMPS?

texts:
I am working on boost converters for switching mode power supply . How can I get knowledge on transient mode boost converter ?
As I know there are different topologies named CCM , DCM and TM which means Transient Mode .

Thanks


texts: Needed help in drawing CMOS design and euler path p-tree ,n-tree for boolean function

texts:
I have the expression \$Z=(A(D+E)+(BC))'\$, I'm trying to draw CMOS logic but I guess I've gone wrong somewhere.
I'm unable to draw Euler path for this diagram


texts:
I want to use multiple CR2032 batteries in parallel for higher capacity in a wireless RF remote (1.8-3.8 V working range for the RF MCU).

CR3032 is an option but I rejected it due to price and availability concerns. CR2032 cells are readily available and cheap.

Since primary cells shouldn't be charged, I feel that some circuit has to be in place to avoid it.

Is it feasible? If yes, what are my options?

Is there a standard part that I can put on each battery? This part should have a negligible voltage drop and should block reverse current.

Diodes are the standard parts that come to my mind but I fear they will take away a big chunk of operational capacity.

Below is the discharge graph of a typical coin cell:

Is it advisable to use a 220 mV schottky diode for reverse polarity and reverse current protection?


texts: How can I add "standoffs" to elevate a SMD component above the PCB?

texts:
I made a mistake when creating a symbol/footprint for a small (2.0 x 1.6 mm) SMD crystal and didn't notice until the prototypes didn't work. Unfortunately, the boards are tiny and expensive (0.4 mm WLCSPs, 0201 passives, etc). I need to use these existing boards for development and testing.

To fix it, I can rotate the crystal 90-degrees and solder it to the existing pads. The problem is that the metal case could now contact some vias and perhaps a nearby guard trace. These features are covered by solder mask, but I don't want to rely on the mask for electrical isolation.

So I want to raise the package up off of the board by 4 mils or so (~100 um) and solder it in place.

As of now, I'm envisioning cutting pieces of copper foil and placing them on the pads with solder paste, then placing the component on these risers (with additional paste). Although I have a (cheap) rework station, this will be difficult: the package covers the pads, the pads are only 0.55 x 0.65 mm, and they won't line up perfectly:

Seems like there might be a better way! Anyone have any good ideas for me? I'll need to modify 4-5 boards.


texts: Not getting appropriate output voltage from the sensor circuit. Is the Flex sensor damaged or am I doing it wrong?

texts:
I want to interface a flex sensor to my PIC18F and I am facing some trouble doing so. The flex sensor is a resistance based sensor, so I am using a voltage divider circuit with the appropriate fixed resistance to obtain the voltage outputs from the sensor. The below are the images of the circuit I simulated in Multisim.

Here is the link to the datasheet of this sensor:
http://media.digikey.com/pdf/Data%20Sheets/Spectra%20Symbol/FS%20Series%20Flex%20Sensor.pdf

The above image shows a close up view of the flex sensor.

Now the problem is:

1) When I rigged up the hardware for the simulated circuit, I noticed that there is a drop of 4.85V across the sensor, for a flat resistance of 10K while it should give 1.667V. And bending the sensor does not show any variations. Therefore I am getting wrong output.

2) Then to verify the sensors Flat resistance, I connected its both the terminals to a meter and noticed that there is no resistance being displayed on the meter, even after varying the meter to check from 200 ohms to 2Mega ohms, but it displays nothing.

From, point one I presume that, I may be doing something wrong. From point 2 I presume that (since the sensor is pretty old), the sensor may have got damaged.

However, how do I come to these conclusions and is my circuit right? and how to check if my sensor is working fine?. Any advice's regarding this would be helpful. Thanks in advance.


texts:
I have written a simple SPI slave on an ATMEGA328PB.  It mostly works, however, I can't seem to get the first byte to be what I want.  The difference between the first, second, and all other attempts is also confusing me.

The master pulls the SS line low, waits 500us, then clocks out 15 '0xFF' followed by a '0x00', waits another 500us, then releases the SS.  Simultaneously the AVR responds with its 'payload'.

#define F_CPU 8000000L

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdint.h>

#define togbit(port,bit) (port) ^= (1 << (bit))  // XOR

// SPI variables
volatile uint8_t received = 0;
volatile uint8_t cnt = 0;
volatile uint8_t incoming[16] = {0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA, 0xFA};
volatile uint8_t payload[16] = "ABCDEFGHIJKLMNO";

uint8_t spiCom(uint8_t data)
{
    SPDR0 = data; // Put current 'payload' into outgoing buffer
    return SPDR0;  // return incoming byte
}

ISR(SPI0_STC_vect)
{
    incoming[received] = spiCom(payload[cnt]);  // Transfer a byte

    if (incoming[received] == 0xFF) // start clocking out data when receiving 0xFF padding
    {
        cnt++;
        received++;
    }

    if (received >= 16 || incoming[received] == 0x00)  // reset array position counters if buffer overflows or received NULL
    {
        received = 0;
        cnt = 0;
    }
}

void initSPI(void)
{
    volatile char IOReg;  // Ignore compiler warnings about me...I'm needed to clear a flag
    DDRB |= (1<<PINB4);  // Set PB4(MISO) as output
    SPCR0 |= (1<<SPIE)|(1<<SPE);  // Enable SPI Interrupt and Slave Mode with SCK = CK/4

    // Clear SPIF bit in SPSR by accessing the SPI registers
    IOReg = SPSR0;
    IOReg = SPDR0;

    sei();
}

int main(void)
{
    DDRB = 0x00; // all of PORTB is input
    initSPI();
    DDRB |= (1<<PINB0);  // LED I/O is output

    SPDR0 = 0xC8;  // pre-load something identifiable into SPI buffer

    while (1)
    {
        togbit(PORTB, PINB0);  // Blink LED while waiting for SPI interrupt
        _delay_ms(1000);
    }
}

The first attempt at communication, the master receives:
0xC8,A,B,C,D...etc.

The second attempt at communication, the master receives:
0x00,A,B,C,D...etc.

The third and all subsequent communications, the master receives:
A,A,B,C,D...etc.

These signals were verified by my logic analyzer.

I can almost accept how the first attempt goes, since 0xC8 is what I pre-load the SPDR register with (as a test).  That said, I still found this behavior unexpected, so I must be misunderstanding something in the SPI section of the AVR's datasheet.

I cannot wrap my head around what is happening after that.  If my misunderstanding has to do with the order with which the SPDR register (buffer?) is handled during communication, I still can't figure out the difference between the second and third (and all subsequent) communications.

I've read just about every SPI on AVR tutorial I could find, but can't figure out where I am going wrong.  Any advice would be much appreciated.


texts:
I am having some trouble in reversing the direction of a sensored 10KW BLDC motor.
Motor has 36 stator teeth and 40 magnets (20 pole pairs)

Apparently the hall sensors position is set for CW direction, and when rotating the motor CCW, the timing is wrong and efficiency is low.

Timing cannot be adjusted in controller (Kelly controller), so I am re-positioning sensors.

The problem is, that while for CW rotation sensors are placed inside stator slots(see image below),

...for CCW correct position (measured with an OSC) position never matches a slot.
Motor manufacturer tried to place sensors for CCW rotation like this (illustration, ignore zip tie):

This looked ok unloaded, but was creating a lot of heat and consuming too much power as I increased load.
I assume this is because the sensor is placed halfway between magnets and one coil, and therefore shows zero reading when coil polarity is same and stronger than magnet passing in front of it - Can anyone validate this theory?

The new placement I am experimenting with to solve this is under the magnets on the bottom side of the motor, with the 3 sensors 6 degrees apart on one small plate, facing the magnet narrow end:

Haven't tested this under load yet, but unloaded test shows the following behavior:
While testing unloaded at 20v, RPM increases as current increases up to around 2A, then when increasing throttle more, current drops to around 1.8A, and RPM increases as you increase throttle up to the expected max RPM for voltage.

This also happens on the CCW motors with sensors on top of stator.

On CW motors, current gradually increases to 3A for max RPM.

Can anyone tell why this is happening?

I would appreciate any comments on this arrangement and possible solutions.


texts: How to select a diode for a Baker clamp?

texts:
What are the requirements when selecting a diode for a Baker clamp circuit?

How does the reverse leakage current of the diode affect the circuit? Can a diode with relatively high reverse leakage current (e.g. in mA range) turn the transistor on spontaneously?

In case of single Schottky Baker clamp, is there a scenario where lower Vf is not desirable, or do we always want the diode Vf to be as low as possible?


texts: I have test a condition when reference voltage(5V) from an ECU is not there. The ECU uses the supply voltage and internally generates the reference voltage using voltage regulator. The reference voltage is use for sensor/switches. I have to test for condition when the reference voltage is not available. My thinking was connecting a resistor to output of the reference pin and lower the resistance until the regulator cant sustain the current ouput.  Is there any other way of going about this?


texts: Are low ESR SMD capacitors with jumper wires between their legs and the circuit OK?

texts:
I have a board with two super low ESR SMD electrolytic capacitors which came off the switching power supply of a notebook motherboard. The legs of the capacitor are still soldered on the board. One of them has a capacitance of 47uF, the other of  560uF.

With both, I have managed to create two sort of legs by soldering two wires in place of the original legs.

In order to restore the capacitors onto the board I need the jumper wires to be a bit longer than the original legs (some 2-3cm each).

My question is:
would this extra length in the connection cause trouble in the circuit? Would the parasitic inductance / capacitance generated be low enough that I get away with this fix in both cases?

Please find below the relevant pictures:

Please let me know. Thanks.


texts: Trying to pull down 1.2V Dataline to GROUND, Does not fully drop to 0V

texts:
Im trying to pull down a 1.2V dataline to 0V with a STM32 development board (H743ZI).
The impulse is only some nanoseconds long, about ~50ns (longer duration or constant: does not matter same result.)

I checked with an oscilloscope: If I ground the connection with the microcontroller the voltage only drops to ~0.6V, which is not enough to reach low logic level.

The line I am talking about is an control line between CPU and RAM. My intentions are to interfere these control lines to stop certain commands. So I have two outputs contending against each other.

New Info:

The RAM Chip ist an Elpida X5116ADSE-3C-E (datasheet). There ist nothing connected between RAM and CPU. So it is just a line without a resistor or capacitor, between RAM and CPU. Just my STM32, the CPU and RAM. I try to interrupt an request pin which is just an input pin. So the line is not bidirectional. And my STM32 is running at 3.3V.

My setup:

I put an 8 ohm resistor in between the dataline and the microcontroller.
I connected ground of circuit board to my microcontroller ground.

What could I do? Do I need to change something in my setup or should I use an FPGA for things like this? What is the problem I can not fully ground the line ?

This is my code, not sure if it matters.

GPIOF->ODR &= ~(1 << 13); //PIN 13 => 0 => LOW
GPIOF->MODER |= (1 << 26); //PIN 13 => 01 => OUTPUT

//17 cycles @ (2ns @ 480MHz) => 34ns
while(counter < 4){
    __NOP();
    counter++;
}

GPIOF->MODER &= ~(1 << 26); //PIN 13 => 00 => INPUT

My schematic (do not have eagle installed sorry.)


texts:
I need to use a projector for a presentation (about 30 mins, but I'll need to make it about 3 times), but there will not be any wall outlets available. I thought about using an inverter and a 12/24v battery (auto?), but I'd like to know if there are any easier options, or if I'm missing something in my original idea.
The projector is a BenQ MS612ST, it has/needs a power supply of 100-240 VAC and consumes 275W.
Can anyone help? Thanks so much in advance!


texts: Is the damage on this circuit board too much to be fixed? (pics inside!)

texts:
So a few weeks ago, my boyfriend's 32" flat-screen TV popped like a firecracker while I was watching it (and scared the hell out of me!), followed by a burning smell. This is the third device of his to fail on my watch (the first and second being his hard drive and a lightbulb, which I recovered and replaced respectively)... It's just a string of bad luck, but I couldn't help feeling guilty, even though they failed through sheer coincidence and no fault of my own (honestly!).

I unscrewed the back panel and took a look inside. At first, I thought that it was just a popped resistor and some damage to the nearby connector. Upon further inspection, however, I noticed there's another spot on the bottom of the PCB that's popped and burned through. Also note the puffy capacitors, which probably caused the cascade of failures.

My primary question to you guys is: Can an average electronics specialist with standard soldering tools fix/replace all of the components that are damaged on this board? Or is it too far gone to attempt a repair without highly specialized equipment? Also, I've heard that some companies can make you a PCB given a schematic diagram... Think I could just ship this to one of them and have them make me a new one? :)

If so, my secondary question is: What kind of connector do I need to replace the damaged one? It's a linear 10-pin connector (as you can see in the picture), with a spacing of 2.25mm. Can I use any connector matching the shape and pitch requirements as long as I have a matching socket piece? And what kind of crimping tool do I need for the pins? I'll probably have to cut that whole end off since it's damaged.

Forgive my ignorance, as I'm a computer scientist and not an electrical engineer, but I'd just like to know whether it would be worth my time learning how to fix it, or if the whole thing should just be trashed.


texts: Poor low frequency response of CD4060 IC

texts:
I have a question that involves a CD4060 ripple counter.

My project is to design a counting circuit that turns off a relay after two hours. This can be done simply using an Arduino, but no microprocessors can be included.

I am using a CD4060 ripple counter with an RC oscillator (I attached an image of the configuration). The output starts deviating from the (expected; I'm assuming) square wave and starts resembling a capacitor discharge at stage 10 and gets worse every stage after.

So here are my questions:

The capacitor I'm using is a monolithic multilayer ceramic chip cap, is this an appropriate type of capacitor to use as a timing cap?
I have seen multiple equations for calculating the oscillation frequency throughout the web. Overall, it's \$1/[(2.x)*(C)*(R)]\$. The first quantity is labeled 2.x because I have seen 2.2, 2.3, and 2.5 ... so I am wondering which of these numbers it actually is?
I have read that the deviation from the square wave is due to a poor low frequency response. Can this be confirmed? Are there any possible remedies for this issue?


texts: What does "shift keying" mean in the context of digital modulation?

texts:
English is not my native language and I do not understand why the words "shift keying" were used to describe some types of digital modulation.

What does "keying" mean in the context of signals and modulation? I know what a key is: something that unlocks a door or a password but I have no idea what does the verb "keying" mean in this specific context of modulation.

What do those words mean individually in this context and what do they mean together in this context?

My question is one about terminology more than about electronics. I understand what Amplitude Shift Keying (ASK) is now. What I do not understand is what is the meaning of the words "shift keying" and why this type of modulation was not named simply "amplitude modulation"?

In none of the Wikipedia articles that contain the phrase 'shift keying' and from the context I do not understand why were those words used. What I understand is 'moving a key' I do not know how is this related to modulation or to electronics in general.


texts:
I have a 250 VA UPS, and I have a couple of devices I want to run on it, a radio (7 watts) and a fan (55 watts). How do I calculate the required battery size (ampere-hours) (for a 12 V car battery)?

And to ensure the UPS is good for those devices, do I just calculate the sum of the load watts (55 watt + 7 watt < 250 * Power Factor) so this UPS can run those devices?


texts:
Is a four point probe applicable for resistance/impedance measurements at high frequencies?

Is there a more common technique for AC resistance/impedance measurements?

Background:
I'm coating fibers and trying to characterize the coating and make sure it's close to the base material and the coating process didn't mess anything up.  I've setup my four point probe for DC measurements and that works fine but now I'm interested in AC measurements as well.  Instruments to measure voltage and current at high frequencies are more expensive so I was wondering if there was another way.

Edit for comments:
@George Herold - I'm interested in conductance and it's the Kelvin four point probe

@Oleg Mazurov - I'm interested in the skin effect.  We're trying to demonstrate our coated fibers do better than a solid wire, at least on a by mass basis.


texts: Drawing Out Circuits from SPICE Description

texts:
I've become familiar with ngspice on Linux (Fedora 15). I even got syntax highlighting going for .sp files in gedit. However, when I describe the circuit in a SPICE deck I have no way of telling whether I'm even describing the correct circuit. Even if I get some kind of output or result, I may have connected a circuit element to the wrong node, which would give completely different results.

My question is if there is some kind of tool that takes a SPICE decks and draws the circuit described in them?


texts: 24v to 12v truck cigarette socket wiring

texts: Hi guys i have a aerpro 24v to 12v reducer, but it has a positive a negative and an earth wire i need to wire it up so i can plug it in to a 24v truck socket and then have the 12v going to a cigarette female end any ideas on how to go about this? P.s i already have the male cigarette socket. (https://i.stack.imgur.com/rqvfB.jpg)


texts:
Find the differential equation relating \$v(t)\$ and \$i(t)\$ of the AC circuit in the following figure.

My approah:
Considering the inductor:
$$ v(t) = L\frac{di_{L}}{dt} $$
$$i_L = \frac{1}{L}\int v_{(t)} \,\mathrm{dt}$$

Considering the capacitor:
$$i_{C} = C\frac{dv_{(t)}}{dt}$$

$$\therefore i_{(t)} = i_{L} + i_{C}$$
$$i_{(t)} = \frac{1}{L}\int v_{(t)} \,\mathrm{dt} + C\frac{dv_{(t)}}{dt}$$
$$\frac{d^2v_{(t)}}{dt^2} - \frac{1}{C}\frac{di_{(t)}}{dt} + \frac{1}{LC}v_{(t)} = 0$$

Is this correct? Please correct me.


texts: Verilog: is connection without wires possible?

texts:
I am sorry to ask this question, which I believe is very basic, but I cannot find an answer. The following example clearly works. But I would like to omit the declaration of the wires ay and by.

module sub(output reg y);
endmodule

module top(input wire sel,output wire x);
wire ay,by;

sub a(.y(ay));
sub b(.y(by));

assign x= sel ?ay:by;

endmodule

Modules have a names. It is possible to address their ports directly? if yes, what is the correct syntax? This does not work (in Quartus)

module sub(output reg y);
endmodule

module top(input wire sel,output wire x);

sub a();
sub b();

assign x= sel ?a.y:b.y;

endmodule


texts: Logic probe circuit; what is the use of some of his components?

texts:
I found this schematic on the Web and I built the circuit but,
due to space constraints, I removed some components and it work well.

I've not mounted the two diodes \$D_3\$ and \$D_4\$ and the capacitors.
For the logic gates I used a 74LS00.

The questions:

What is the purpose of \$D_3\$ and \$D_4\$?
To protect the supply in case of fault in case I connect the probe at high voltage?
And what is the use of the two capacitors?

Thanks in advance.


texts:
I'm designing a small home weather station. I've got a bunch of popular sensors like BMP180, DHT22, DS3231 clock and so on. Luckily most of them are I2C, so I won't have to use too much wires, but I decided to create a PDB and ask some company to create it.

I'm having hard time to learn Eagle, but I managed to create appropriate packages, symbols and devices. I also netted everything. Don't mind the mess, this is my desperate attempt to force Eagle to make valid connections.

However, when I create board from the schematic, Eagle seem to transfer connections in some weird manner.

Notice the capacitor, despite its connection to NRF module, on board it's connected with other components.

Also, when I run the auto router, it seem to ignore connections to Arduino Micro completely:

What am I doing wrong?

Edit - changes

I did as suggested and named all nets. I'm quite certain I did it correctly, because each time I named the net the same as one coming of other pin, Eagle asked me, whether I want to connect them.

This is how the schematic look now:

However, autorouter still ignores connections to Arduino despite - as it seems from the screen - being aware of their existance:

The question stays the same - what am I (still) doing wrong? :)


texts: ATtiny13A - Can't generate software PWM with CTC mode

texts:
I'm trying to make a remote control RGB LED light using an ATtiny13A.

I know the ATtiny85 is better suited for this purpose, and I know I might not eventually be able to fit the whole code, but for now my main concern is to generate a software PWM using interrupts in CTC mode.

I cannot operate in any other mode (except for fast PWM with OCR0A as TOP which is basically the same thing) because the IR receiver code I am using needs a 38 kHz frequency which it generates using CTC and OCR0A=122.

So I'm trying to (and I've seen people mention this on the Internet) use the Output Compare A and Output Compare B interrupts to generate a software PWM.

OCR0A, which is also used by the IR code, determines the frequency, which I don't care about. And OCR0B, determines the duty cycle of the PWM which I'll be using for changing the LED colors.

I'm expecting to be able to get a PWM with 0-100% duty cycle by changing the OCR0B value from 0 to OCR0A. This is my understanding of what should happen:

But what actually is happening is this (this is from Proteus ISIS simulation):

As you can see below, I'm able to get about 25%-75% duty cycle but for ~0-25% and ~75-100% the wave form is just stuck and doesn't change.

YELLOW line: Hardware PWM

RED line: Software PWM with fixed duty cycle

GREEN line: Software PWM with varying duty cycle

And here is my code:

#ifndef        F_CPU
    #define        F_CPU        (9600000UL) // 9.6 MHz
#endif

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

int main(void)
{
    cli();

    TCCR0A = 0x00;                        // Init to zero
    TCCR0B = 0x00;

    TCCR0A |= (1<<WGM01);                 // CTC mode
    TCCR0A |= (1<<COM0A0);                // Toggle OC0A on compare match (50% PWM on PINB0)
                                          // => YELLOW line on oscilloscope

    TIMSK0 |= (1<<OCIE0A) | (1<<OCIE0B);  // Compare match A and compare match B interrupt enabled

    TCCR0B |= (1<<CS00);                  // Prescalar 1

    sei();

    DDRB = 0xFF;                          // All ports output

    while (1)
    {
        OCR0A = 122;                      // This is the value I'll be using in my main program
        for(int i=0; i<OCR0A; i++)
        {
            OCR0B = i;                    // Should change the duty cycle
            _delay_ms(2);
        }
    }
}

ISR(TIM0_COMPA_vect){
    PORTB ^= (1<<PINB3);                  // Toggle PINB3 on compare match (50% <SOFTWARE> PWM on PINB3)
                                          // =>RED line on oscilloscope
    PORTB &= ~(1<<PINB4);                 // PINB4 LOW
                                          // =>GREEN line on oscilloscope
}

ISR(TIM0_COMPB_vect){
    PORTB |= (1<<PINB4);                  // PINB4 HIGH
}


texts:
I'm trying to construct an SMPS power supply with 230VAC at 50 Hz input and 5.6V/2.5A output. Here is the schematic:

The design was optimized with EE19 core selected and I am expected to optimize the power supply with EE16 core to save space on board. The problem is that, as PI expert simulation indicates, maximum flux density limit exceeded.

1) What points should I take into account to solve this problem?

2) Is there any recommended book, or resource to understand the theory better?

I've just worked on PS unit; so, I really appreciate any comments whether it is related to my problem, or not.

Thanks


texts: PIC18F13K50 Has two or one Half Bridge control?

texts: Since the PIC18F13K50 has one ECCP, and it can operate in single, full and half bridge, I dont undestand if it can drive 2 half bridges at the same time, or just one...it appears to be just one though...


texts: Noise sensing microphone in the ANC circuit has three terminals

texts:
I am trying to understand ANC practical implementation from a headset in which ANC has been implemented. The microphone which senses the noise has three terminal. I have only seen microphone which has two terminal (one for power and signal other one for ground).
The image attached below is a microphone marked as A. I am unable to understand, what is B. What is the use of B in picking up the noise.

The second image shows back portion of the PCB. It has three terminals, one should be for power and signal other one should be for ground. What is the third wire doing here.


texts: Can't Get Raspberry Pi and Xbee to Work Together

texts:
I am having the hardest time trying to get my XBEE's to work with my Raspberry pi (RP). I have one on a USB breakout board into my computer and the other XBEE connected to a RP. The one on the RP is the API coordinator and the one in the computer is the AT router. When I run this program on the RP (which should change one of the IO pins on the router XBEE)

    #!/usr/bin/python
import serial
print("TEST")
ser=serial.Serial('/dev/ttyAMA0', baudrate=9600)
print(ser)
ser.write('\x7E')
ser.write('\x00')
ser.write('\x10')
ser.write('\x17')
ser.write('\x00')
ser.write('\x00')
ser.write('\x00')
ser.write('\x00')
ser.write('\x00')
ser.write('\x00')
ser.write('\xFF')
ser.write('\xFF')
ser.write('\xFF')
ser.write('\xFE')
ser.write('\x02')
ser.write('\x44')
ser.write('\x01')
ser.write('\x05')
sum=(0x17+0xFF+0xFF+0xFF+0xFE+0x02+0x44+0x01+0x05)
check=(0xFF - ( sum & 0xFF ))
ser.write(chr(check))
ser.close()
print("DONE")

Nothing gets done on the router though. I believe the XBEE's are connected because when I plug in the router to the computer, I get a message on the serial port the RP notifying it that something has joined. I am out of ideas, and I was hoping someone could help me out.


texts: Op-amp theory vs practice: what have I done wrong

texts:
I'm currently trying to use the MCP6142 op amp in an ultra-low power project (sub-uA ideally). This op-amp has been chosen because it has the highest GBW in the set of the sub-uA op-amp we've reviewed. However in the range of the frequencies we'd like to amplify (3800-4000 Hz) the gain of this op-amp is far from "ideal". See this figure from the datasheet:

So we've come up with this circuit to amplify the signal:

simulate this circuit – Schematic created using CircuitLab

Considering the following equations:

Vout = G(w)*exp(j * phi(w))*(V+ - V-)
V- = R1 / ( R1 + R2 + 1/(jwC1) ) * Vout

We've derived the transfer function H(w):

H(w) = G(w) * (1+j*w*(R1+R2)*C1) / (G(w) + j*w.*G(w)*R2*C + exp(-j*phi(w)) + exp(j*(pi/2-phi))*w*(R1+R2)*C);

We've used G(w) and phi(w) plots from the datasheet to compute H(w) and plot its curve:

So we expected a peak gain around 4000 Hz... that we never observed when pluging a waveform generator at the input of the op-amp. Of course, we tried to find the peak by tuning the waveform generator frequency, but we never found it. What could we have done wrong? Have me made a good use of the Gain-Phase plots from the datasheet?


texts: How do I calculate the duty cycle range for DC-DC buck converter?

texts:
Question:
A buck converter supplies power to a microprocessor with a core voltage of 1.2 V and peak power requirement of 2A. The supply for this buck converter is a lithium battery with a nominal voltage of 3.7V (range 4.2 full to 3.0 V flat).

Assuming the converter operates in CCM, what is the duty cycle range as the battery discharges? Both switching devices will be MOSFETs each with less than 30 mOhm on resistance.


texts: Given The Same Load, Will A Larger Inverter Generator Burn More Or Less Fuel?

texts:
I'm looking to buy an inverter generator for backup of a few essential devices during power outages.  I've already tested for & calculated my required wattage (including starting wattage where applicable).  Still, I'm debating over size:

On one hand, buying a higher wattage generator would give me more leeway to add additional appliances in the future if desired.  But on the other, if I don't end up needing the extra wattage, it would consume more fuel & therefore effectively shorten my "off-grid" time limit (given a fixed stockpile of propane).

...Or would it?  This is my actual question:

Given the same load, would a higher-wattage INVERTER generator burn more or less fuel per hour than a lower-wattage one? For instance, let's say I run a load of exactly 1000 watts. Will a 4000-watt inverter generator burn more fuel per hour than a 3000-watt inverter generator on a 1000-watt load?

On one hand, it seems like the bigger one might burn more due to it having a physically larger engine.
But on the other hand, it seems like the bigger one might burn less, as it's farther away from its max output & can therefore throttle down & work less hard. I've asked a couple manufacturers and searched around online, and have gotten conflicting answers.


texts: How to connect J-link OB to an RF transceiver module?

texts:
I'm looking to program the RFM380F32 RF transceiver module which includes an ARM Cortex-M0+ processor: http://www.hoperf.cn/modules/soc/RFM380F32.html
The documentation suggests programming in Keil and using J-Link OB for debugging and flash download. The module is brand new and I was unable to find an evaluation board.
I'm wondering if matching the VCC, GND, SWDIO, SWDCLK pins on the J-Link to the same pins on the module will suffice or if I need to add resistors or other components for the connections to SWDIO and SWDCLK.


texts: Why does the USA use 110V and UK use 230-240V? What are the advantages? Explain me with calculation. Why do they use different frequencies like 50Hz, 60Hz? What is the reason?


texts: Why are regenerative logic circuits called regenerative? I know that regenerative means to generate again, but why is this word used to describe circuits like flip flops and latches?


texts:
I usually use my Arduino as an ISP programmer.

Let's say I want to program the blink LED code to my ATmega328 with the bootloader already in it.

Can I just program it in the classical way and pull out the chip from the Arduino? Is there any problem doing like this? It sounds easier and quicker.

(I'm talking only about ATmega328 with the bootloader already in it, not ATtiny or other ATmega chips.)


texts: Microcontroller's JTAG interface and PCB

texts:
I'm about to start making my own microcontroller circuit (using an Atmega series MCU, at least for the beginning) and I think I'm gonna get the AVR JTAGICE JTAG debugger & programmer.
I also plan on making my own PCB lab at home so I was wondering - based on your experience - if it was better to use DIP packages or SMD (SOIC, TSSOP, TQFP/LQFP).

As far as I understood DIP packages are preferred in the D.I.Y. sector, whereas SMD are better because they take less space and should be less sensible to electromagnetic interference (for instance with other ICs).

Now to the question: if you need to (re-)program the microcontroller, which one would you use ? AFAIK there are two alternatives:

Use a DIP socket soldered to the PCB and put the DIP MCU in there. Whenever I need to reprogram it, I take it out of the socket, put into an adapter-like board to JTAG, reprogram it and transfer it back to the socket
Put a SMD component on the PCB and let a JTAG port accessible from the exterior (should be 20 pins, right ?). I'd also like to keep the circuit as small as possible, so are there any low-footprint headers with 20 pins ? Sorry but I don't know how they're called exactly. It doesn't need to be JTAG really: I can leave a low-footprint header there, go onto an adapter PCB with a cable and go to the debugger via the official JTAG cable.

I think the first solution is the simplest and probably a bit cheaper. It should even be easier to solder.
What do you suggest ?


texts: How improve temperature sensitivity of HP 721A DC Power Supply voltage reference?

texts:
I have a sentimental affection for my HP 721A DC Power Supply:
http://hpmemoryproject.org/pict/wall_a/anim/721a_q90/viewer.htm

Rugged, dependable, and roughly as old as I am, it is also pretty temperature sensitive. At the high end of its voltage output (30V), it can easily drift 700mV from morning turn-on (~19C) to the late afternoon heat (~25C).

I believe this is primarily due to the primitive-ish emitter-follower-based voltage reference circuit is uses:

(full schematic here: http://www.kennethkuhn.com/hpmuseum/scans/hp721a_sch.gif)

V.ref is -V.zener + V.BE of the Germanium PNP (Q4) and has a temperature variance of roughly 26,000 ppm over the course of the day's temperature variations.

I was thinking to submit one of my five specimens to experimental surgery to see if I could improve the temperature sensitivity without disrupting the rest of the circuit. (The sentimental affection I mentioned combined with low eBay prices have ended with me "adopting" a number of these units :)

No need for excessive precision; a circuit with a TC in the hundreds of ppm would be a huge improvement. I'd like something with discrete components if it would work with say two or three transistors. I'm also considering a highish-precision low-voltage reference (~1.22V) buffered with an LM358 op amp with gain of about 6, but wanted to avoid the possible need for compensation gymnastics if a simple-ish discrete circuit would give the improvement I'm looking for.

What options might one recommend?


texts: High side current sensing in BLDC motor?

texts:
I want to measure DC current flow through the 48 V battery in bldc motor (through Inverter circuit). Are INA 282, INA 169 work properly or not? Since my battery motor specification is 48 V, 5 Amp, 250 Watt

Previously, I used ACS 712 current hall sensor but it nor worked. Its reading was totally absurd.

If any one have any idea regarding this, please help me.


texts:
Is it possible to wire the LED's in the following way??(shown in the rough diagram of my circuit)

I want the LED's flashing alternatively, ie - D1, D3, D5, D7 (A LED's) are powered by just the transistor and the rest (B LED's) are by the op-amp and transistor (op-amp inverts the signal making it flash alternatively)

The switches are to control the "shutting" of a row and column in order to have just one LED blinking. That is if only LED D3 should be blinking Switch 1 and Switch 2 should be closed, with the rest of the switches open.

my question is: Is it possible to connect the LED's as shown in the figure??

and in order to switch just LED D3 ON, SW1 and SW2 are used, use of SW1 would also switch LED D1 ON, how do i avoid that??

Thanks!

simulate this circuit – Schematic created using CircuitLab


texts:
My power supply is filtered regulated 5 volt 500 mA . I am using a 555 in monostable mode to switch the motor on for a certain amount of time after the 555 is trigerred. (The 555 is being trigerred by a counter circuit). But the output current from the 555 is too low. How can I use a transistor like 2N3055 to get full 500mA current? What other ways are there to achieve the same thing?

Will this work?


texts:
I'm trying to snowman some BGA pads in eagle but not coming across any real way to do it. Theres the teardrop.ulp but for whatever reason it doesn't add any teardrops to my pads.

Is there an easier way?

edit
An example of "Snowmanning" compared to teardrops


texts: How can I keep my sinusoid in phase with its input after filtering?

texts:
A section of a circuit I'm working with makes a sinusoid from a square wave by passing it through an 8th order filter (MAX293). Up until now, everything was ok, but I was told recently that the input (square wave) and output (sinusoid) have to be in phase. Because of the LPF, it adds a phase shift and because the input frequency is variable (0-5khz), the phase shift is also variable.

How can I keep them in phase for the entire frequency region they operate at ? What should  I be looking at ?


texts: In Proteus 8 simulation of the PIC16F84A assembly code (.asm), any setting (BSF) or clearing (BCF) of the pins  clears pin RA4!

texts:
After a thorough investigation, it turns out that the Proteus 8 simulation of the PIC16F84A (and possibly other MCU-s in PIC16 family) has a bug when interpreting the assembly language code, which happens either the source code is put directly in Proteus, or its compiled hex or cof form is read into the device.

THE OBSERVED BUG IS as follows:

-- any setting (BSF) or clearing (BCF) of PORTA pins <3:0> will inadvertently RESET the pin 4 on the same port, that is: RA4 will turn to 0 if it was previously set to 1.

Picture 1 contains the assembly code, where the instruction comments (even of those which are commented out) explain the errors.

For example, if the RA4 is set to 1 (in line 29), and after that the RA3 is either set to 1 or cleared (and in this case it doesn't matter if it was already 0), RA4 will be cleared.

Picture 2 shows the state of the debugging simulation immediately after the instruction BSF PORTA, 4. In the bottom of the window, the binary state of PORTA is displayed, showing that the pin 4 is set:
PORTA = 00010000

Picture 3 shows that after the following instruction, BSF PORTA, 3, the pin 3 is set as desired, but also that the pin 4 is cleared by mistake:
PORTA = 00001000

The cause is probably the wrong binary mask for the PORTA in the simulation, or the improper logical treatment of the mask and the previous contents of the PORTA.

A FEW MORE OBSERVATIONS

The same code executed in the MPLAB IDE simulation (MPLAB SIM) runs as expected.
RA4 pin is of open-drain type, in difference to the pins RA3:RA0, but the error is happening on the logical level of simulator, so the bug has nothing to do with that.

THE WORKAROUND

The problem could be solved by setting the RA4 last, that is, after all the RA3:RA0 pins are set or cleared. This further confirms the  hint that the problem is somewhere in the handling of the bit mask.

QUESTIONS

Has anybody else encountered the same problem?
Is this bug fixed in the later versions of Proteus 8?


texts:
I'm hitting a snag plotting some data with ngspice.  I'm not sure of the syntax to use to add a title.  According to the user manual:

General Form:
plot exprs [ylimit ylo yhi] [xlimit xlo xhi] [xindices xilo xihi]
[xcompress comp] [xdelta xdel] [ydelta ydel] [xlog] [ylog] [loglog]
[vs xname] [xlabel word] [ylabel word] [title word] [samep]
[linear]

The title argument is used in the place of the plot name at the bottom of the graph.

That syntax is a mouthful.  Dutifully using the above: plot db(vo / vin) title Stage_1_Gain.  No dice.  I'm not really seeing a title anywhere on my plots.  According to the manual, it should be on the bottom.  All I've got is my axis labels.  Is there a mistake in my syntax somewhere?

Edit:  Also no dice using a string, plot db(vo / vin) title "Stage 1 Gain".


texts: How to use SCR to control the power of a heater

texts:
I would like to point out that I am not an expert (as it is perceived by the question) in the use of scr, diac, and triac and that this question is more for academic purposes than use in real life. Basically, I need to better understand how the scr is commonly used.

I wish to understand how to use SCR in a dimmer with a given heater resistance value and an input voltage frequency value. My goal should be to fully understand how I should pick the other components and if the schematics that I provided below are right or wrong.

The first schematic is very simple. The RC part should activate the SCR during the positive halfwave of the input. For R very small the SCR should be almost always active during the positive halfwave while for R very large the SCR should be almost never active during the positive halfwave. It is correct what I wrote? How should I pick the values for R and C? Supposing I want to keep the SCR active for a given percentage of the positive half-wave, how should I act?

simulate this circuit – Schematic created using CircuitLab

I saw on on schematics that I found on internet that almost all add a diac before the gate of the SCR. What is it's purpouse? How does it change things? I think that is to not stress the gate of the SCR but I'm not sure.

simulate this circuit

Furthermore, in some cases there is a diode from mass to gate. I think that is because in the input negative half-wave the SCR isn't used but, again, I'm not sure that this is the real and only reason. If a triac is used instead of the SCR the diode is obviously absent.

simulate this circuit

I know that a real schematic should be much more complex but, for now, I'm interested in keeping it as simple as possible in order to fully understand.


texts: Is there any way to draw power from a cellphone?

texts: If so how would you do this? I know you can get a little power from the headphone jack, but is there any other way? is it possible to draw power from the charging port? Or is this charging port just and input source only? How much power would be available and under what conditions?


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I'm looking at the LM4881 headphone amplifier. The amplifier uses an inverting OpAmp style set up.

What is the effect when audio gets inverted?

Will a difference be noticed or do we hear inverted audio all the time and never notice?

Should there be a second inverting stage to keep the audio the same?


texts: What is the purpose of a mains X2 Security Capacitor and how to determine its value?

texts:
simulate this circuit – Schematic created using CircuitLab

I am evolving an existing circuit which has a 230VAC input.
The 230VAC has multiple loads:

Transformer followed by rectifing circuit;
Small DC motor 3.6W.

There is an X2 security capacitor of 0.22uF across the 230 VAC input.

I am not sure of all the reasons to have this capacitor.
Q1: What are the reasons to have an X2 security capacitor?

I suspect that it is required for the DC motor.  However, the specification of the DC motor says that it requires a 0.1uF/10% capacitor @230V .
Therefore the existing 0.22uF X2 CAP seems to be historical and out of the required range.
If this corrects the power factor, then a 0.22uF could overcorrect this.

Q2: How to determine the value of the X2 security capacitor.  (Should I change the capacitor to 0.1uF).


texts: Please help explain how OVP works using voltage divider

texts:
I tried to convert an old 12.09V LiteOn power supply to an adjustable voltage power supply by installing a pot to change the voltage divider for its TL1431C shunt regulator.   I was able to make it change output voltage between 5V and 13.84V (the capacitors on the output side are all rated 25V).  Anything more than 13.84V will cause the power supply to shut down (output ~ 0V) due to OVP.  I found this information about OVP in the datasheet of the SMPS control IC used in this power supply.  Can you please explain how this OVP works without a known reference voltage as in the case for TL1431/TL431?  Thank you very much.
https://www.nxp.com/docs/en/data-sheet/TEA18361T.pdf
OverVoltage Protection (OVP)
An accurate output OVP is implemented by measuring the voltage at the AUX pin during
the secondary stroke. As the auxiliary winding voltage is a well-defined replica of the
output voltage, the OVP level can be adjusted by the external resistor divider ratio
R AUX2 / (R AUX1 + R AUX2 ).

On my actual power supply, there are only 2 resistors 15 KOhm (153) and 100 KOhm (1003) that are directly connected to the AUX pin.  To add insult to injury, these resistors are also connected in parallel, resulting in a resistance of about 13 KOhm (as expected) at their two ends.  I expected to see two resistors in series to form a voltage divider around the AUX pin. Even if these two resistors were in series, their actual values would still not make any sense.  I could change the pot to increase the output voltage to about 13.84 V before OVP kicked in and shut it down.  I wanted to increase the upper voltage limit using the formula:
ovp_limit = 3.0 * (Raux1 + Raux2) / (Raux2)
Or is there a way to just disable OVP altogether?
I do not yet want to remove these tiny SMD resistors prior to being able to understand properly how their values are calculated to produce the upper voltage limit.
There's a post about OVP voltage divider using another IC LTC4364 for which its datasheet provides a very clear example:
Setting Over voltage and Under voltage limits for LTC4364
For my case, the NXP TEA18361T datasheet and the actual power supply parts are just totally confusing to me.


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I am analyzing a buck regulator circuit as shown in following figure.

link for datasheet given here:
http://aosmd.com/pdfs/datasheet/AOZ1014AI.pdf

I have few queries in schematic:

Q1. In above schematic, IC U16 is getting burned  unexpectedly by getting hot.
Can someone suggest me the solution?
Is there any flaw in design?

Q2.Why two inductors are connected here, because in datasheet and standard buck regulator, there is only one inductor.

Please suggest, how can prevent IC from burning and malfunctioning ?
Thanks in advance. :)

PS. "Lamp" signal to EN pin is coming from Microprocessor (5V).
    & Vin is 12 V DC.


texts: Charging 2x Li-on 18650 Batteries In Series

texts:
I am on a battery powered project where i use 2x18650 batteries connected in series.

I bought this specific module 2S Li-ion Lithium Battery 18650 Charger Protection Board Module

What kind of charger do i use for this?Could i solder usb connections to charge the series through this module with 5v?

I admit i don't really know how this module works.Does it isolate each battery to completely charge it and the move on to the next?


texts:
I have a small situation, A = Outside light, B = Porch light, C = Inside Light.
I would like to switch

A + B together but not C, and then

B + C together and not A

Is there a relay or something that would switch between two different control to achieve this ?


texts: Measuring current and internal impedance of current source

texts:
I am building a current source for an EIT project that I am doing. I have not reached the multiplexer part as I am still having issues with my current source. I am developed the current source as shown below.

It works on my actual circuit board, but the bipolar waveform does not appear on my multisim simulation.

I am supposed to get my non-inverted sine wave output from U2B, and my inverted sinewave from U1A. These sine waves are then passed into U4D and U3C which are configured to be the howland current source exactly at 1k ohms.

My main issue from this is how am I able to measure the current out from U4D and U3C into the water tank of my EIT project. I need to get around 1mA passing through the water tank. I have tried using a variable resistor as my load, but I am unsure how to calculate as U4D and U3C has a bipolar output.

If there is also another possible way to calculate the internal impedance, I would also like to know.

Thank you