texts: Low-cost way of shining a wide line of light, kind of like some bar code scanners do

texts:
What is a cost-effective way (say roughly $15) to shine a wide but thin beam of light, directly away from the source, so that it would project a line onto a nearby surface?

My particular beam would need to be about 4' wide and maybe 1mm-4mm thick. The light would not necessarily need to be parallel like a laser, but needs to be pretty focused (1-4mm) for the full range between 1" and 4" from the source, so that if an object is moved within that range, the beam projected on it is always thin, and fairly parallel so that ~0.25" bumps on the object would not block parts of the line.

I considered using a strip of SMD LEDs behind an acrylic lense that is concave along the thin axis, and plano (straight) along the long 4' axis, at a distance such that the light focuses to a line in that 1"-4" range...but that would probably be a long focal length, which would require more space than I might have. Also the LEDs would need to be spaced such that the overlap of each LED's contribution makes the line fairly even in intensity. But before going that direction, I wonder if there is a better solution.


texts:
I was thinking if a current is applied to a metal door handled and somebody touched it that should complete the circuit to ground and be detectable but I'm not sure if this would work as the 'somebody' most likely will be wearing rubber soles and even a rubber glove. But if it was sensitive enough it might work?

Can anybody suggest a circuit maybe using current as I mentioned or capitance (increasing the capacitance by touching the handle made part of capacitor) or inductance (deviative a coil by touching the handle made part of an inductor)?

Or something else that is triggered by touching the metal handle?


texts: How to prevent a Lipo/Li-Ion-Battery from catching fire after a complete self discharge with a following accidentally recharge

texts:
From the following Youtube video (at 3:15min) I got that it is dangerous to recharge a Lipo/Li-Ion-Battery after it was completely discharged (0V), because it will catch fire.
https://youtu.be/1rg3ZWxBNUE?t=194
I'm using the following circuit. It cuts off the load at 2,5V, but then there is still the self discharge, which leads the voltage down to 0V volts by the time:

Is there a common or established way to prevent recharging a completely discharged battery, which is fitting to the circuit from above?


texts: First SMD Design Comments / Input before Manufacture

texts:
Just designed my first "real" PCB that I plan to send out for manufacture in the next day or so.  I've milled out a few on a 3018 CNC.  I wanted to do this one that way as well, but realized it would have been a bear to make DIY and mostly THT wasn't the direction to go.  So, this is my first mostly SMD PCB with standalone ATMEGA328P-PU on a PCB at least. I used Diptrace initially, but then switched over to EasyEDA since I plan to send it to JLCPCB for the best cost and all their components from LCSC have the included the PCB footprint.  (Side note: I wasn't looking forward to switching at first, but the component selection with included pattern was a real treat with EasyEDA compared to Diptrace).
Purpose:
This should actuate servos to control water flow to "zones" based on the feedback from the sensors of soil wetness.
I am a complete novice to this, but I think that the design is close.  I learn by doing and iterations, so here goes.  I figured you guys love this stuff and it is second nature to you, so I am all ears for any general feedback, criticism, and design improvements in general that I will take to my future PCB design endeavors and use this one.
The PCB Layout:
the components on the right will be exposed from the enclosure for user feedback, and the JST XH connectors are for the sensors.  There is a DC 5.5 x 2.1 plug for a 12V 1A DC adaptor in top left.  Key 1 is a "test" button that I plan to use to prime this thing. SW1 is the power switch. The U components connect to sensors for feedback that will be evaluated in the code.  The H headers are connected to servos that respond in accordance with the settings provided by R1, R2, R3.  H4 is ICSP header for programming.  P1 is the motor.  I increased the mil trace to 15 mils for the power and ground lines. U2 is the 5V regulator.
Edits: Added ground plane, moved decoupling capacitors for the MCU closer to their point-to-point, added some decoupling capacitors to the adapter feed.  Increased trace widths to 24 mils (same as via diameter).  Removed interior mounting holes that were too close (shouldn't be needed).

Specific Questions / Schematics:

Is 4 and 5 for SW1 like chassis grounds / PCB grounds?  I can just leave them unconnected right?
Do you see U2 having any issues with regulating the 12V 1A supply for the 5V Reg that is provided downstream to all the other applicable components?  In breadboard testing, amperage never really exceeded 500mA, but since the supply could provided 1A, I chose a "larger" package regulator.  MC7805BDTRKG - Datasheet
Oscillation, Stabilization, and ICSP look correct?
The test button will pull PD7 (Test Net Port) to ground when depressed right and 3, 1 can remain unconnected?

Thanks in advance!
THT Layout:


texts:
How do you program a sleep mode for your Arduino?
Especially for battery powered designs, what are good techniques for sleeping the CPU but waking up only when needed?


texts: What’s this slim rectangular box on my utility pole?

texts: It’s the silver box on the utility pole here:


texts: Test load capacity of cable & clips with only constant current/constant voltage power supply?

texts:
I want to test a 20m wire and soldered alligator clips on each end to see if it can carry the needed current I want to use it for (eg 5A.)
Can I just hook it up to the terminals on my bench top (lab style) power supply that has constant current / constant voltage dials, essentially shorting the power supply, but use the constant current mode/control to stop anything bad happening to the wire or PSU by excess current?


texts: What can cause oven’s heating element to deform?

texts:
What can cause a heating element to deform this way?

My oven is tripping the breaker whenever I turn on the heating, LCD and light are working fine, the front LED flickers though!
The model of the oven is IKEA Framdit OV9.
One of the elements has 30 ohm resistance and the other has 60, and given the data on the elements they have 1650 and 800 Watts power rating respectively. So for 230v they resistance seems be fine.


texts: What could be generating this waveform in an EMC Compliance test?

texts:
We are having trouble with a CISPR-11 (EN55011) Radiated Emissions Class B compliance test in one of our solutions. The troubling part of it is basically an industrial motherboard (with a commercial SSD and commercial RAM) within a well grounded metal enclousure, sharing space with an industrial switch, a switching 12V industrial power supply and a industrial touch panel and monitor. Every single one of these industrial components have its corresponding compliance certificate for CISPR-11. The antenna picks up the following waveform (Vertical orientation, 3mts distance, 30 to 200 MHz bandwidth). Crosses above the threshold are non-compliant peaks.

The main offender is a 60MHz peak that looks like a strong square wave in frequency domain. That is new to me in these tests; I am more used to specific harmonics in the spectrum.
If we turn off the motherboard (and thus also the RAM and SSD), the 60MHz and also those crests at ~80MHz dissapear. Turning of the rest of the components (except the 12V PSU) has no effect.
I have the motherboard's compliance test and procedures, and their peaks are nowhere near in power or frequency. They also used commercial RAM and a mechanical commercial hard drive.
Has anyone seen this waveform before for radiated emissions and/or has any idea, given the description of our system, what could be generating it?
EDIT: Based on comments and answers, I will clarify some things. First, I have 1 Ethernet cable (unshielded) inside the case, connected to the switch, also inside, but then 3 Ethernet SSTP cables going out from the switch to 3 ethernet Basler cameras. These 3 do have a ferrite clamp on each, but I haven't fiddled with the one inside. I'll note that down.
The SMPS was our main target for the whole ordeal but I still need to try ferrite beads on its outputs and maybe enhance the shielding around it.
Unfortunately we do not have our own spectrum analyser and our scopes are up to 60MHz. We do not develop high frequency custom electronics, so they were not neccesary. Given the circumstances, we may adquire one and do our own pre-compliance testings, as many of you suggested.
I will keep this updated.


texts:
this is a graph of v-i relationship of a battery (not ideal one since it has internal resistance)

as you can see, the slope is 1/R, so as time passes by, R increases, therefore, the slope approaches 0. the graph now tend to become horizontal in time, so the open circuit voltage increases in time. but in real life, when battery ages, the open circuit voltage it has should be decreasing, why is then the graph and my intuition dont agree?

this is based from my experience since as i measure the voltage in an old battery, i find it lower than the expected voltage like a brand new one. thanks


texts: How far does a PCB antenna need to be from a capacitive sensing touch button?

texts: From my basic understanding, capacitive touch works by having a small voltage applied to a touch plane on a PCB, resulting in a uniform electrostatic field. When a conductor (human finger) touches the uncoated surface, a capacitor is dynamically formed and a touch is detected due to this change in the capacitance. Now, if I wanted to have an RF antenna (dipole) near a capacitive sensing plane, would there be any issue for either the antenna or the touch plane? If so, how far apart would they have to be to mitigate any major loss in efficiency?


texts: Is it safe to look at the IR LED clusters on security cameras that are commonly available? They seem to be quite capable of lighting up a distance of 6m. What is their energy density? I'm not sure if it'd be reasonable to assume 150mW/sr. A cluster of 12 such LEDs would mean 1.8W/sr.


texts: Transformer test only making sense unloaded

texts:
I have a problem in testing a transformer recovered from an old wall wart. The transformer has several secondary taps: the wall wart had a slide switch allowing the selection of four different dc outputs via a bridge rectifier and capacitor.

I connected the ground clip of my oscilloscope to the transformer wire that had connected to the common of the switch, then connected the probe tip to each other wire in turn to measure voltages. The resulting voltages made sense, for example a 10.6Vrms waveform was measured for the tap that had provided 12Vdc.

The problem arose when I tried to measure the voltages under load, as in the previous measurements I had simply placed the scope across the secondary taps directly.  To do this, I connected a 1k resistor across the highest tap (10.6Vrms as above).  This was a light load and well within the maximum rated secondary current of 1A.  I then connected my scope across the resistor. I expected to see a somewhat lower voltage under load, but measured a flat 0V.

I can make no sense of this result, and feel it must be a basic misunderstanding. I have tried other smaller and larger loads of 10k and 100R with the same result.

Below is a diagram of the setup. I am omitting the other secondary taps.

simulate this circuit – Schematic created using CircuitLab

Edit: The comments helped me to resolve the issue.


texts: Should I use a mechanical or solid state relay for a hairdryer

texts:
I have a device that needs to use a controllable source of hot air. I want to use a hairdryer as they're available everywhere and very cheap too.

I have a board with these relays on it (and I'd be happy to be able to use it :))

I am in the EU now and the hairdryer would be 220v / 1500w so the specs below should work.

but the main question is:

Should I use a mechanical or solid state relay for this kind of load?


texts: Extending an HDMI port or Display cable?

texts:
I am working on building this project for my Raspberry Pi well I need to extend the HDMI port of this monitor http://store.hp.com/us/en/pdp/hp-22er-215-inch-display

I need to place the display in an enclosure, so the horizontal HDMI connector with a regular cable would cause the case to be too deep. So I need to basically relocate the port onto a breadboard and then connect to my raspberry pi. Any ideas? I was considering desoldering it and attempting to get wires to lineup and connect to it. Or somehow extending the ribbon cable coming from the board to the monitor so that I could put it in a separate box or something.

Any suggestions on if it would be a better option to extend the HDMI port or somehow extend the display ribbon cable?


texts: Why will the line loss decrease when the power factor increase?

texts:
QA:

If the  line loss  is \$50\ kW\$ when P.F. is \$0.8\$, now if P.F. become \$0.95\$, what is the value of line loss?

Solution:

\$\frac{P_{L2}}{P_{L1}}=\frac{(cos\theta_1)^2}{(cos\theta_2)^2}=\frac{(0.8)^2}{(0.95)^2},\$ so \$P_{L2}=P_{L1} \times \frac{(0.8)^2}{(0.95)^2}=50\ kW\times \frac{(0.8)^2}{(0.95)^2}=35.45\ kW\$

I have two questions about this:

1.Why is \$\frac{P_{L2}}{P_{L1}}=\frac{(cos\theta_1)^2}{(cos\theta_2)^2}\$?

2.We can know the unit of line loss is watt\$(W)\$, that is, the line loss is a real power, not apparent power or reactive power. So if the P.F. increase from 0.8 to 0.95, that means \$\theta_1 > \theta_2\$, the real power shouldn't change, but apparent power or reactive power will decrease because of the decreasing of \$\theta\$

However, my second thinking should be wrong, because the answer of the QA does decrease with the increasing of P.F.

There is a figure about my second thinking:


texts: Wirelessly connect several DS18B20 across a house

texts:
I am planning on reading temperature data form across my home using several DS18B20s and sending all of the data to a raspberry pi. I have already managed to interpret data from one sensor directly wired into the pi, but I'm having trouble finding a way to wirelessly connect several of them.

I have looked into products such as this rx tx pair, but I don't think that it can communicate two ways and I believe that the DS18B20s needs to both send and receive. I have also looked at this transceiver, but it looks like it uses a lot more ports than I want to, and I'm not sure if it can transmit the single line of data that I need to without all of the other wires/ports. I'm basically (I think)looking for a transceiver that only communicates the one wire that I need without all of the extras(if this even exists/is possible). I feel like I'm missing something that is very obvious, but can't seem to figure out what. Here is the DS18B20 data sheet if it helps. Thanks in advance.


texts:
We know in an SCR when in conduction mode, triggered by some gate voltage, the lower three junctions will essentially turn into a single N junction and so the SCR essentially becomes a PN junction diode type element.
Is it safe to assume after conduction starts and onwards that the SCR's VI characteristics will be the same as that of a diode? Because the VI graph of an SCR looks like a PN junction diode when conduction starts.


texts: Is it possible to fully charge a 12V lead-acid traction battery using a car battery charger?

texts:
I got a 45Ah 12V traction battery for my experiments and I was assuming that I can recharge it using a normal car battery charger (the main difference between 12V car starting battery and 12V lead-acid traction battery being that traction battery is more deep-discharge resilient and support way more cycles).
But there is some information label on battery that say there are 2 different charging methods for 2 different use cases, which confused me:

Stationary use: charging voltage 13.6 - 13.8V
Cyclic use: charging voltage 14.5 - 14.9V

Max charging current: 13.5A

The microprocessor controlled car battery charger I have is using 4A charging current, so I guess it should work, just might be a bit slower, but I am not really sure how the lead-acid battery charging process works. Is that charger going to recharge the battery until some predefined target voltage, or is it using some sophisticated calculation to figure out if battery is really charged to 100%?
I would like to avoid car charger stopping the charging process at, say, 50% of actual battery capacity, because I noticed that different 12V lead-acid batteries, seem to have different voltage at "full charge". How is this full charge determined? Is this car battery charger going to work for this, or do I need some special charger?


texts: A question about measuring white noise in practice

texts:
I have some confusion about practical aspects of dealing with white noise.

Let's say you want to quantify or view the white noise component of a power supply output or a constant transducer output. How is the white noise component be extracted from a measured signal in practice? Such a measurement can be done by a scope or data acquisition sampling.

But white noise power spectral is constant over infinite frequency. But how can such a signal as white noise be sampled then? If it has infinite bandwidth what should be the minimum sampling frequency when sampling white noise? Or it doesn't matter?

I know the sampling theorem but this white noise is hard to grasp when it comes to practice. Again an example would help. Let's start we have a 9V power supply and we have access to its terminals. One can see the switching noise from the FFT of the logged output signal as long as sampled at least twice the switching noise or more ect. But suppose one wants to verify the white noise component, what could be done in practice?


texts: Can I charge a lipo battery using piezoeletric energy harvesting?

texts:
I use a 9V 800mAh lipo Okcell battery to power my ESP8266 ESP-01 with a voltage regulator to change it to 3.3V. I use the ESP to detect the voltage peak from a piezoelectric when someone is running to measure the force and determine the time someone on air from the voltage graph.

The current consumption of my ESP8266 is about 75mA. From my understanding the battery can power my ESP8266 for about 8 hours because of the 20% power loss from the voltage regulator.

So for my project, can I use the piezoelectric to power my battery while im not using it. The piezoelectric I'm using is PZT type. I want to a use a force amplification frame for the piezoelectric so I use ANSYS simulation to simulate it.

Of course the data is not 100% correct but I still cannot measure the voltage and current generated from the piezoelectric as I still did not fabricate it yet.

So is there any way to use the piezoelectric to power the battery theoretically speaking. It doesn't matter if it will take 1000 hours or not, my supervisor just want to know if it still can do.


texts: Female headers for breadboard (or: how do I extend the pins of my breakout board?)

texts:
Where do I find female headers with pins just long enough (~6mm) to fit a breadboard?

Ordinary socket headers such as these:

have pins that are too short to stay put in the breadboard, but the so-called stacking headers such as these:

have pins that are too long and too thin.

I sometimes have breakout boards with parts underneath (they are meant to be plugged into another board with socket headers), which I want to be able to use on the breadboard. The male-female extension wires from Adafruit are great for momentary checks, but not for something that might last a few weeks on the breadboard.

I can't find anything on Mouser, and even since Digikey stopped having a printed/PDF catalog, it's impossible to find anything unless you know the exact part number.

I know I can get the stacking headers and trim them, but there has to be a tidier solution.


texts: How do you make a usb device thats just an accelerometer

texts: So I'm trying to do this with as few components as possible. Also, If possible I would like to skip the microcontroller all together. So how would it be done with a triple axis accelerometer? Any chance you could point me in the right direction and tell me what I would need to start with/learn and where I would need to go there


texts: What is the role of the pull-down resistor in a diode-transistor logic (DTL) gate?

texts: What is the function of R3, and what happens if we operate the circuit without it?


texts: GPS taking long time to fix out in the open

texts:
I am trying to use a ORG-1411 GPS (https://origingps.com/products/hornet-org1411/) to get location and UTC fix, using the breakout from Mikroe (https://www.mikroe.com/nano-gps-click). To parse the readings I am using ublox ucenter (https://www.u-blox.com/en/product/u-center) and sometimes I also use TinyGPS+ library for the Arduino.
The TTFF was around 5 minutes for location and 10 seconds for UTC time the first time I turned on the GPS from cold start. I expect the fix time to be lower (< 35 seconds) as claimed by Origin for the subsequent cold starts (https://origingps.com/wp-content/uploads/2019/09/Nano-Hornet-ORG1411-Datasheet-Rev-4.3.pdf). However, the GPS takes the same amount of time to get the location and time data from satellites. I tested the module in two locations out in the open with open sky above and no surrounding buildings within close proximity.
Can anyone suggest what's wrong?


texts: Does lack of MMU make any difference for applications?

texts:
Generic Linux can't be run on Cortex M3 because Cortex M3 has no MMU. Okay, there're special versions of Linux that can run there.

The problem is I don't quite get how this affects application software.

Suppose I have some application - any user application, let it be ZIP unpacker as an example. I have it in source form and can compile it for ARM.

Will it run on Cortex M3 that has no MMU? How do I know if lack of MMU will affect any given program?


texts: What is the purpose of a resistor in the feedback path of a unity gain buffer?

texts:
I often see unity-gain followers with a resistor in the feedback path.  For an ideal op-amp, of course, there is no current into the input, and this resistor does nothing.  What is its effect with a real op-amp, and how do I choose its value?

What does R1 do in this circuit?


texts: I am trying to integrate a DC tension with a classic op amp integrator. The problem is : when I simulate my circuit on LT Spice, the output will always be equal to the VEE tension of the op amp regardless of the 1/RC coefficient. If anybody can help me on this problem, I put the circuit and the graphics below.


texts:
I am using a mosfet and an Arduino and I want to control the Source-Drain current of the mosfet by adjusting PWM to the Gate.

If I apply zero value to the PWM, the current doesn't stop (I checked the PWM output with voltmeter and it's zero volts). When I manually connect the gate to the ground with a wire, the current stops.

How can I stop the current with PWM output that connected to the gate?

Here's my circuit. I common all the grounds with wire and put mosfet and hall effect sensor on two separate breadboard.

Also, I'm powering the Arduino with a printer cable that's connected to my laptop.


texts: Wiring up a Knitter-Switch rotary encoder

texts:
I have two MERP 12 24 126 GR rotary encoders from Knitter-Switch. The only information i can find regarding this encoder is here http://www.knitter-switch.com/pdf12/E-2012-MER12-MERP12illuminated.pdf

However I'm not able to figure out which pins needs to go where except for the output ABC pins. Where do i connect GND and VCC? Does it needs both etc?

Through testing it appears like pin 1 is GND (at least for the LEDs) and pins 2 & 3 are the two LEDs. I havn't been able to get any output from A, B or C at all.


texts:
What is "balanced" audio exactly, and why is it useful? I've read that it means there are two voltages, with one being the inverse of the other. A balanced audio receiver looks at the difference between these, and calls that the "signal". Noise should affect both halves of the balanced signal equally, so the receiver should not see noise as signal, because it does not change the difference between the two halves.

But this doesn't make any sense. Isn't an unbalanced audio signal also a difference: the difference between ground and the signal voltage? Why can't we just feed an unbalanced audio signal into a balanced audio receiver and call it balanced?

And how does making a second, inverted voltage change anything at all? If we didn't do this, wouldn't noise still affect both halves equally, and still be rejected by the receiver?


texts: How are solar spectra simulators used and are they used to test photo-diodes and image sensors?

texts:
For example here is link to a Xenon lamp solar spectra simulator Xenon lamp AAA Class Solar Simulator.

Two spectra are shown in the plot given in the link, one for the AM1.5G reference an other of the solar spectra simulator itself. If one needs to test e.g. an image sensor or a photo-diode signal produced from sunlight in 800 – 1100 nm range what is the benefit of using a solar simulator, since spectra in that band (800 -1000 nm) does not resemble the sunlight spectra at all. Actually it looks like a complete mess after 700 nm, and far from a good fit to the real solar spectra or AM1.5G.

Since other solar simulators I have looked up have a similar spectrum I don’t understand how are they used ? Are they used for testing photo-diodes and image sensors, that is to simulate the signals produced by the certain sunlight spectral bands at all, or I am missing the purpose of solar simulators ?


texts:
I was working on a project regarding building a high power LED driver as a excitation light to excite the florescence in the plant tissue. I want to turn the LED on and off at around 200Hz~10KHz.I came up with the following circuit:

After finish building the circuit, I want to measure the voltage across the LED. First of all, I am not exactly sure if the way I measured is correct. I put the two probes in the anode and cathode of LED separately and use math function in oscilloscope to subtract it and then I got the wave form of voltage across the LED. BTW, I don't have differential probes.

The waveform I expected to get should be when I turn the MOSFET off, the voltage across LED should be 0 and when I turn the MOSFET on, the voltage across LED should be almost like 14V.

However, I end up getting something like this:
I apply the PWM signal to the gate of the MOSFET at 200Hz shown below(yellow wave)

Then the green wave is LED's cathode and the blue wave is LED's anode shown below

After using math function subtract it, I got the pink waveform like this:

As you can see here, the LED seems does not fully turn off. When the MOSFET is off, there are still some voltage across the LED.

Anyone familiar with why it causes this problem? Anyone has any idea how to solve this problem and to modify the circuit?Do you have any other way to drive and turn the lexuon rebel LED on and off?

I appreciate any help you can give to me!

The LED I use is luxeon Rebel Royal Blue(three of them in series )

The MOSFET I use is STP14NK50ZFP


texts: Bleeder resistor: switch resistance on when capacitor is powered off?

texts:
Possible Duplicate:
  How to discharge smoothing capacitors?

I have an aluminum capacitor (~600-800uF) smoothing a DC current (~60-70V, ~50-70mA). I have a resistor in parallel to drain the capacitor when powered off.  It is important that this capacitor is drained quickly (under 3 sec) when powered off and also that it provides maximum power when powered on.

I've learned that using a lower resistance drains the capacitor quicker but sacrifices running power as wasted heat. On the other hand, a higher resistance provides optimal power and minimal heat but simply drains the capacitor too slowly.

Is there a simple (cheap and small) way to switch a resistor on only when the capacitor needs to be drained? This way maximum power can be achieved and the bleed time can be precisely controlled.

Thanks!


texts: What is this unusual LCD controller technology?

texts:
Preface: Even if you do not have a definite answer, I would greatly like feedback from anyone who has even seen an LCD using this technology.

I recently took apart a Canon digital camera from the late 1990s and obtained an unusual LCD display. Unlike the standard chip-on-glass controller technology used on modern LCDs, this one appears to have the chip embedded in the glass.

Here is the camera in question, a Canon PowerShot S100 2MP Digital ELPH:

Link to Amazon: http://www.amazon.com/Canon-PowerShot-Digital-Camera-Optical/dp/B00004TS16

It appears to have first been sold on Amazon on September 4, 1999. I cannot find any other information about when it was released.

When I took the display out, I noticed that the metal bezel around the display was only about 4mm on each side, and the flat flexible cable attached directly to the glass with no room for the standard controller chip. The display appears to have been made by Sony, as seen at the top left of the bezel and on the back of the display.

I decided to remove the metal bezel, backlight, and filters and still could not find a controller chip. However, there was a black area around the display that appeared to be painted onto the top layer of the LCD, which made me curious as to what it was covering up. I decided to remove the top layer using the following procedure that has worked for me with other displays:

Remove the top and bottom polarizers from the display.
Score the center of the top of the display with a sharp tool
parallel to the connector.
Put the display in a plastic bag to aid with cleanup.
Place a flat-head screwdriver over the center of the display
parallel to the connector.
Hit the handle of the screwdriver with gradually increasing strength
until the top layer shatters.
Remove the display from the bag and remove the shattered top layer.
Clean the display to remove small glass fragments and the gel-like
substance between the 2 layers.

It worked and I was able to isolate the bottom layer. The controller integrated circuit appears to be embedded in the glass and distributed around the outside of the display. Here are some very close-up pictures:

I can not find any information about this technology on the internet, even just something saying that it exists. Does anyone here know what it is called, why it was used instead of chip-on-glass, when it was used, and if there is any information out there on it? Has anyone out there even seen this before?

Related question, if anyone knows why: Why do LCDs used in cameras have the pixels in a staggered arrangement (see my photos up close or look at a camera LCD yourself)?


texts: Do I glue the screw when mounting the PCB to enclosure or not?

texts:
Well, this is a handheld device we are developing at our firm. We bought the enclosure from a chinese man. in AliExpress. It's made out of ABS. The device is going to be used in an industrial site. The board pictured below is a UPS-like board that charges the battery and will have an adapter jack. Here are the PCB board mounting requirements:

Fastening the board so that it does not release in case of free fall or using extra force by personell while pluging the charging adapter.
Being able to quickly replace the board with a new one in case of component failure.

I intended to use glue inside the screw hole and tried CA and SR based adhesives, but they are uselss. CA-based glue is rigid and SR-based glue is not that hard.
What would you suggest?


texts: What sort of filter is in this old TI application note?

texts:
I'm trying to analyze a circuit from the ~40 year old TI TMS9928/29 Interface to Color Monitors application note.  It shows how to convert the (almost) Component video straight from the graphics chip to RGB or Composite out.

All three of the YUV video lines have what is presumably a filter (with identical component values) that I wasn't able to find in any of the filter recipe lists in AoE or elsewhere:

(I'm guessing C14 is an unrelated coupling capacitor.)

It looks vaguely like a low-pass filter, but tinkering around in LTSpice, I wasn't able to make the output look any different than the input (above, at, or below the ~3MHz signal frequency).

Walking through the application note schematic is pushing the limits of my analysis ability (in a productive, trial-by-fire sort of way), but this one has me stumped.  Thanks!

EDIT: Of course it's not filtering the voltage; that whole top rail is the same node!  (This is how you can tell I need more practice.)  Wikipedia says "the parallel RC circuit is generally of less interest...", so maybe a better question is "Why did the TI engineers put those components there?"


texts:
So pretty much I have a ~4.5V power supply from 3 AA batteries, that I want to power an op amp (LM358P).

The reason I'm doing this is so I can boost the AC signal from a piezo sensor, the problem is, every time I set it up correctly (I think), without the signal inputs, it gets really hot, I've read the data sheet and kinda get whats going on.

I'm also not too sure how to hook up the signal, do I connect one cable to ground and one to the non-inverting, or do I connect it to Vcc-?

Thanks for the help y'all.


texts:
Recalling this question:
Choosing series resistors for zener diodes

I thought to open a new question related to this, because it is centered to a specific part of the old question.

It is said that, when a Zener of a given voltage is used with a lower current than the tested one, it provides a smaller zener value. I tried with the BZX84C3V3 and applying 5V with a 560Ω: I have a bit more of 3.3V, which is reduced when using 2.2kΩ. Does the zener cut the voltage better (or even to a low voltages than 3V3) when derated in current?

This is coherent with the datasheet, but I don't get the logic: doesn't the Zener shall be less opened to GND with lower current? And being less open, more zener resistance shall be present and according to the voltage divider, I shall see an higher voltage. Instead, it is happening the opposite.


texts: Would using step-up and step-down converters in the same circuitry damage the battery?

texts:
One of my projects, to be powered by 2S Lithium Ion batteries (7.4V), requires various voltages, such as 3.3V, 5V and 12V, to be derived using a couple of step-down and a step-up converter.
I am apprehensive on the use of a step-up converter after the negative feedback I have received.
However I would like go ahead and use it based on the advice of more experienced people in this forum.
Details of the step-up converter are accessible here.MT3608


texts: Designing a common-emitter amplifier circuit

texts:
We are asked to design values for RC, RE, R1, and R2 for the following common-emitter BJT amplifier:

It's easy to calculate RE and RC:

But I couldn't find a way to design values for R1 and R2. So how can I do that?


texts: Determine the working frequency band of unknown RFID chip

texts:
I have a passive RFID chip from which I would like to scan the ID.

I have a standard USB RFID Reader, but this doesnt print out anything. This reader scans the 120–150 kHz range, so the chip must use another range.

Before I buy another reader device I would like to find out what is the range in which the chip operates?
Is there a cheap way to find this out? If yes, how?


texts: I have implemented a schematic for an IC (BGM13S32F512GA-V2R) and I am trying to create a footprint but when I try to place the padstacks, they do not appear in the default library... so I went into the settings and added a link to my directory with priority over the standard library. They are still not showing up.


texts: What are good materials and associated tools for a robotics hacker?

texts:
What is good stuff to quickly build small hobby robots?
What sorts of tools do I need to work with those materials?

Let's assume we already have the electronics parts listed at
"What is a general set of components for a robotics hacker?",
and focus on all the other parts and tools.

material for rigid frame (what type?)
material for outer skin (waterproof?) (what type?)
wheels (what type?)
legs and feet (what type?)
gears and belts (what type?)
attachment methods: nuts and bolts, glue, zip ties, etc.

I'm looking for stuff like "Acrylic is nice, I recommend X thickness, you need Y to cut it to shape and Z to attach the pieces together"
and "cardboard is nice for quick prototypes; you can make it waterproof using W".


texts:
Consider a SR latch. I have a doubt in that. why the outputs of a latch are always complement to each other.
Please clarify this to me,take any input and show that P is complement of Q.
Also in textbook they have given 11 input combination is forbidden,so that shouldn't be applied.
What happens if we really give 11 input,do we get output or don't or what will happen?????


texts: (How) can I run a microcontroller and DC motor from the same battery?

texts:
I have a microcontroller (a PIC10F200) that I'm using to control a DC motor. It's a very simple circuit. A button is pushed and the pic sends output for certain increments of time. The thought is to use the microcontroller output to control a hexfet which is controlling a DC motor.

The question is:

(How) can I run the DC motor and microcontroller from the same 9V battery?


texts:
On my board I have to acquire dozens of input digital signals. Each one might be a dry contact or pnp (12V). I have to isolate them from the MCU side.

The basic circuits could be:

dry contact: pull-up resistor to 12V and input across the optocoupler diode

pnp input: series resistor and input between the other end of the resistor and GND

What could be a simple circuit to handle both configurations? It's ok a front-end compatible with both or a single dip-switch to select.


texts:
I trying to use a Li-ion Battery in my project. ICR18650-26H is suitable for my project(GPS data logger) I think. I am having hard time understanding one particular parameter in the specification document of the battery.

My questions are:

Is the internal resistance of the battery a PTC in nature?
If that is the case, i dont have to use external thermistors to measure the temperature of the battery? Or can I use an external thermistor of my choosing?

Thanks


texts:
For a few weeks now I've been trying to construct a joule thief using a schematic commonly found on the web as seen in this url:

It consists of an npn transistor, a 1k resistor, two coils wound around a ferrite core and a 0.5 V battery. I've tried at least 10 different npn transistors that I've salvaged from broken equipment and CFL light bulbs to no avail. I have ensured that the windings are correctly connected where the opposite end is twisted together at the positive supply. None of these attempts resulted in a greater voltage across the Collector-Emitter leads.

I decided to buy a 2N3904 transistor since I have seen that joule thief circuits have been made with them online. Whats different from the circuits I have found online on websites and youtube videos is that I did not connect any led across that Collector-Emitter leads so I then assumed a diode was needed for some reason. However, the diode I connected made no difference, the results were the same. Then I thought that if the cell's voltage wasn't enough to overcome the barrier voltage between the base and emitter so I used a cell with a voltage of 1.5 V however across the Collector-Emitter my multimeter read 0.99 V instead of an increased voltage. I would like to know what I have done incorrectly and why has none of these circuits worked for me. Any suggesting to get this working would be appreciated as building the same circuits online only for them not to work is quite frustrating. Thank you.


texts: What makes this active antenna "active?"

texts:
I'm using a external taoglas GPS/Glonass active antenna. It has a male SMA connector and I don't see where any voltage source hooks up to thing. So how is it active? Or does the power required for the internal active components come in on the signal line (center conductor of connector)?

The datasheet says "active" but I don't see anywhere in the datasheet it talks about it.


texts:
I am going to be amplitude modulating a high power LED light from a peak on a mountain. I want to recieve this faint light as far as physically possible before the light fades out too much to recieve.

What is a practical way with high gain to recieve this light to be amplified for a speaker?

EDIT:
I would like the beam to travel about 2 miles or 4Km from nearby bergen peak visible from my house. Here is a Google Earth image:

AS a 15yr old experimenter, my budget is mainly limited to 75 dollars due to all my other projects I am working on.


texts: Identify/substitute an SMD MOSFET labeled "540N 88KFG" for LCD monitor repair

texts:
I'm trying to repair the logic board of an LCD monitor that died while giving off a burned smell.

It seems that an LCD driver chip and a MOSFET (I think) burned out. The chip was easy to identify (HV9982) and order, but I can't unambiguously identify and find a replacement for the other part.

It is labeled "540N 88KFG" and I think its form factor is TO-252 / DPAK. Below is a photo, there are three of them in the middle of the picture.

A related question is what characteristics I have to make sure to match if I can't buy an exact replacement. Searching around for "540N" MOSFET, I found some in other packages whose main data points were

100V source-drain voltage
33A current rating.

If those do indeed apply to this component as well, what else needs to match in a replacement?

Update: After looking around a bit longer it appears that IRFR3410PbF might be a reasonable replacement.


texts:
I am trying to build a 18w amplifier based on this schematic
however my power transformer doesn't have a center tap on the secondary winding

Is it possible to use this power transformer for this project?
I also tried it using a solid state rectifier (the one with 4 pins: - AC AC +) connecting the ac to the transformer the (-) to ground and the (+) to the standby switch (please see the schema), although I could measure the correct voltage on the (+), there was no current going on the grids of the tubes, not even on the filtering capacitors.

or maybe the problem is somewhere else in the circuit?
appreciate your help


texts: Cheap and simple way so switch on and off based on voltage, with hysteresis

texts:
I'm playing a lot with solar powered systems using ultracaps for energy storage. I'm also powering some small ~3.3V systems directly from LiFePO4 cells, charged by solar power.

In both cases I'd like to be able to power on the load when the ultracaps / battery reaches a specified voltage V(on), keep it on until the voltage falls below a second voltage V(off), and then keep it off until it rises back to V(on). V(on) > V(off)

Ideally, the circuit to achieve this should be as simple as possible (fewest components), cheap and all components readily available. It must also not draw much power itself (max. a couple of mA).

So what would people recommend? I've searched online and found microcontroller based solutions, but this seems like overkill and simple Schmitt triggers, but these don't quite fit the bill either - at least the simple implementation I tried never worked reliably.

Thanks!


texts:
I'm preforming some measurements with a differential probe and I'm not sure what is the correct attenuation ratio I should use (measuring about 300 V voltage drop on a varistor, which is a surge protection device), so I ended up trying them both. I got the more reasonable results using 50:1 ratio, but the thing is I got a measurement of 316 V while the probe's datasheet indicates that the max voltage I should use in 50:1 is 140 V, but while trying 500:1 ratio my results didn't make any sense.

Does anyone have an explanation for that?


texts: Adjustable charge current from programming resistor for Li-Ion charger - how to change on demand?

texts:
I am designing a device which has an integrated Li-Ion battery (single cell, for simple low power portable digital device) and normally charges by way of a buck converter which goes from 12-16V Automotive supply to 5V, then into the single cell linear battery charger. If in the event the battery goes 'flat' and is not desirable to wait and rely on automotive input (inconsistent supply) or during user interaction by for example diagnostics/testing/data logging I need to also power the battery charger IC via the same power bus.

When the buck converter operates, it is intending to charge at up to 1-1.2A if possible during the short times it has energy available. In the normal use case of this device, the buck converter is the primary input to the Li-Ion charger. I will therefore make the standard case for the charge current setting of my charger IC to be 1.2A.

In the case when the USB is connected, it is assumed the device has been removed from the automotive input, but just in case I will have the USB activate the "Shutdown" Pin on my Buck converter IC. The only remaining issue (as far as I can see) is the charger IC attempting to draw 1.2A to charge the battery, from a USB port on a standard computer!

I have come up with a way to have a "normally ON" N-channel MOSFET based switch for a resistor to be in parallel to give me the required R_PROG value for ~1.2A. When USB is plugged in, the buck converter is disabled and the switch which parallels the two resistors is turned "OFF", leaving only the high value resistor and therefore the low (200mA) charge current for safe use with a PC or laptop.

I have attached a picture showing my plan below, which uses a MOSFET, NPN transistor, and 3 resistors to implement my plan. Note the blocking schottky diode D1 for the USB bus to the battery charger input node, that is there for protecting the USB power bus if the buck converter is in operation but the USB bus is not powered/floating, and to make sure the NPN transistor does not then also turn off the MOSFET.

The question is: Is there an easier way that uses less components than my intended N-MOS + NPN + 3 resistors to achieve a context sensitive resistance value for the charger IC, where the resistance is normally low, and when a certain input is connected, the resistance goes higher? This must be done in hardware, for a fast response. Slow responses may attempt to draw too much current for too long.

I am not actually sure if the charger IC can deal with an adjustable resistance like this on its PROG pin, as it may just sample the resistor initially and lock in the charge current setting until power-off. Any thoughts on that part too? The charger is MCP73113/4. Thanks for any insights guys/girls!


texts:
I wish to run an MCU (for bluetooth to be specific) which commonly runs on a coin cell battery. I was wondering if it was possible to replace the regular CR2032 battery with the smaller and cheaper hearing aid batteries (e.g.). The CR2032 has a typical capacity of about 240mAh, and I can see the orange "13" (PR48) battery in the link has a capacity of about 280mAh. Given that the voltage is almost half that of the CR2032, would I be able to replace the CR2032 for 2 of the smaller PR48 batteries in series to get the same result in operation?

I don't know a lot about electronics so please explain why or why not...


texts:
I'v found myself in need of a new preamp for my turntable (the one built into my power-amp went out with a bang and tripped the breaker!).

I'm using a moving magnet type cartridge with output around 5mv, I would like high gain to around 1v peak to peak, must include RIAA compensation and a simple and preferably cheap design with good sound that can be powered with a 'wall-wart' type mains adaptor.

After a little research I found a design by Boozhound Laboratories that is very simple and seems to have very good reviews/reputation.

This is the Boozhound Laboratories circuit (rev3):

So I copied the circuit into LTSpice to see how it would preform, swapping the 2sk170 for lsk170a as I'v heard original 2sk170's are tough to find.

The circuit had less output than I wanted at only about 620mv from a 10mv input (peak to peak voltage) and fairly high distortion at 0.178% mainly all second harmonic.

So I changed the drain resistors to 4.7k witch increased output to 1300mv but also increased distortion to 0.249%:

Unhappy with that amount of THD, I decided to try and do better with my own transistor based design:

Output was good at over 1000mv and distortion was very low at 0.003%.

My amps RIAA curve also looks about right?

My question is shall I go with the Boozhound labs design that has a good reputation, despite its high distortion and use fake jfets, or my own circuit that I'm really not sure on transistor noise, how it will sound and dislike the need for more caps (C1 and C2 for added gain).

I would also like to improve power supply noise rejection. Would a simple voltage regulator (like LM317), capacitors and perhaps a inductor be good enough?

Thank all!


texts: Is this circuit correct for a DC motor driver?

texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to design a basic circuit for controlling both the direction and speed of a permanent magnet DC motor. The way I intend to do this is to use the circuit above (component values are arbitrary) however I have a couple of questions to ask:

Do I need to add an opto-isolator between the Gate resistor and the PWM signal?
If I want to add a fuse for safety purposes in this circuit would I place it between my 24VDC source and the Drain of my mosfet?
What addition could I add to this circuit in order to change the direction of rotation of the motor?
Is there a possibility of changing both the direction and speed of the motor using a wigwag potentiometer (similar to the ones used on mobility scooters) without building something too complicated?

These are the motor parameters:

power rating: 0.43kW

Voltage rating: 24VDC

Full load Current: 18A


texts: Polygon Pour not working in inner layer Altium

texts:
When i try to pour plygon in my inner layer the outline of the polygonis only visible .

Can somebody help me to solve this


texts: What do I need to do to protect connected shift register output pins against shorting?

texts:
Initial situation:

Q1 is HIGH, Q3 is HIGH, Q5 is LOW
D1 is forward biased, D2 is forward biased, D3 is reverse biased
Therefore, Q3 is protected against shorting by D2

Next step:

Q1 is changed to LOW, Q3 remains HIGH, Q5 remains LOW
Nothing changed with Q3 and Q5, so, of course D2 is still forward biased and D3 is still reverse biased
Q1 did change, however, since only a very short period of time has passed, D1 didn't switch yet and is still forward biased as well
Therefore, for a very short period of time, current can flow from Q3 HIGH, through forward biased D1 into Q1 LOW.

Is this true? Is this a problem? If not, why not?

I thought about setting every output pin to LOW for the necessary switching time according to the diodes' data sheet.


texts: three points (two slopes) op amp conditioning circuit

texts:
I'd like to get the output on the right when applying the signal on the left to a signal conditioning circuit using op amps.

I've got different slopes so I guess I need two amplifier circuits with different gains (16 and 24 plus a 2V offset). Even so how do I select one of the two? Using a third op amp used as a comparator? Is there a more obvious solution?


texts: Puzzle: Controlling two lamps with one SPST switch (AC)

texts:
This is the text of the problem:

  Draw a circuit with two lamps & one SPST switch.

  The lamps must be in opposite states.

New parts are disallowed to add to the circuit, but there is no limit on the type of lamps. We can't replace lamps with LEDs.


texts: converting g changes to angular velocity

texts:
I am trying to get angular velocity from accelerometer. I can get G values and degrees of object on 3d space.

Can I convert g values somehow to angular velocity?

I was thinking taking differentiation of angular displacement but I dont know whether it will be accurate or not.


texts: soldering equipment advice for small parts

texts:
For a while I've been fiddling with electronics, designing my own pcb's and soldering a lot of thing together, which is lots of fun. I've become quite comfortable soldering small parts, like 1206 resistors (by hand) and SOT-23 packages (solder paste + hot air).

I now often come across parts that are basically supposed to be used in a professional way, by pick and place machines, for example, parts like TPS63001 (3x3 QFN package)
or the MAX17043G+U (TDFN-8) and was wondering if I should attempt to use them and what would be the best approach.
I know that using parts like those are best suited to be picked & placed in a automated way, but price wise that doesn't really seem to be a option for one off prototypes.

If I want to solder these parts manually, what kind of equipment should I be looking at? (Or should I not attempt using them at all? ) I currently only use a soldering station (a cheap baku) that also has a hot air gun, which is ok, but not perfect, so I was already thinking about buying a proper soldering station (maybe a weller).
Would hot air be a good way to go with these small parts, or should I look at hot-plate soldering or even a reflow oven?
Should I look into some device for magnification? maybe a electronic microscope?
And what about a solder paste dispenser? would it be more suitable than stencils for one-offs?
Any other tools that would be required for this work?

My main problem with soldering paste is currently that I don't have a proper way of putting the right amount on for these small parts. Usually I pot on too much which leads to shorts in the circuit.


texts: Looking for a better understanding of a kilowatt hour and trying to size an electricity supplier using it

texts:
I am trying to design a fuel cell that can provide enough energy for 1 day's use a maximum capacity but I am having trouble sizing the fuel cell because I need a better understanding of kilowatt hours.

I found online that the average power consumption of a house is about 8,900 kW-hr per year which amounts to approximately 24 kW-hr per day.

If I wanted to design a fuel cell, would it be considered a 1 kW fuel cell? I am trying to size it.

The reason I ask is that I read an article and it said "A 3 kW fuel cell ..." so i was wondering if I could just consider this a 1 kW fuel cell and then size it based on that assumption


texts:
I'm looking to raise my blinds every morning
using an rpi/Arduino and a motor. The blinds are lifted by a cord that loops near the bottom. I've checked that the cord requires about 20N force to pull down, and the gear turning the cord loop at bottom will have a diameter of 6 cm.

Which motor should I buy?

Min torque needed ~ 20*3 = 60 Ncm.
Min speed ~  20 rpm


texts:
I'm trying to amplify a sine wave voltage signal by two at high frequencies (20kHz) I've tried using an op-amp as the frequency gets this high the wave turns triangular (I'm assuming this is to do with the slew rate).

Is there another way to amplify this signal across the frequencies of 1-20kHz and keep the sine wave?


texts: Software for PCB servicing, boardviews how they are created

texts:
Boardview files containing information about printed circuit boards, their components, used signals, test points and more (popular in laptop/pc service). These files may have following extensions: .asc, .bdv, .brd, .bv, .cad, .cst, .gr, .f2b, .fz. and others.

I want to generate such file and maybe use some open source software to display them. For example there is software called Openboardview. https://openboardview.org/. I want to generate file for that software, preferably in open source pcb suite, maybe Kicad?
There is software, like openboardview for example, that reads many formats of these files. So it's not so complicated. What is the format of these files?
Maybe there exists scripts, third party tools that can generate such files from circuit, pcb, and BOM file?

Simply, I want to generate files about pcb/circuit/elements for service and be able to use simple viewer like openboardview to display them. I don't want to use whole pcb suite to look at board. Sorry for my english, it's not my native language.

I'm familiar with pcb suites like: Eagle, Kicad, Diptrace, but they don't have options to generate a file for (for example) openboardview.

If software i want is very expensive, maybe exist simple program which can read images of circuit and pcb, and read part list, and i can manually annotate images?

Greetings,

Martin


texts: How do I wake from sleep on PIC10F200 via watchdog?

texts:
So far I have worked with many other micro controllers but not the PIC-family. I'm having trouble with waking from sleep via watchdog on a PIC10F200. I'm programming it in C using the MPLAB X IDE v2.35. All function's an macros are part of microchip's baseline libraries for the processor.

Here is a minimal example of what my problem is:

#include <xc.h>
#pragma config CP    = OFF   // Code protection off
#pragma config MCLRE = OFF   // GP3/MCLR pin fuction is digital I/O
#pragma config WDTE  = ON    // Watchdog Timer enabled
#define _XTAL_FREQ 4000000

void main(void) {
    OPTION = 0 | nGPWU | nGPPU & ~T0CS & ~T0SE | PSA | PS2 | PS1 | PS0;    // bits: 7: no wake-up on pin change; 6: no weak pullups; 5: internal clock; 4: incremnt low to high; 3: prescale on wdt (Timer0 if cleared); 2-0: clock division by 128
    TRISGPIO = 0b00000000; // set all to output

    while(1) {
        GP0 = 1;   GP1 = 1;   GP2 = 1;   SLEEP();  // set all high and sleep a bit
        GP0 = 0;   GP1 = 0;   GP2 = 0;   SLEEP();  // set all low  and sleep a bit
    }
}

Basically this is a classic toggle-pin (blink LED) example using the watchdog. Only the pins are high all the time. What did I do wrong?


texts: Why are pull-up resistors not drawn this way?

texts:
So, I've always been using a pull-up resistor in the configuration that usually appears in textbooks but I can't tell why it isn't drawn in another way.

So, basically a pull-up resistor is usually used to prevent a direct connection between ground and the supply voltage when the input pin of some digital device is to be made LOW. The question is why isn't a pull-up resistor drawn as shown by the circuit on the right? In this way, there'll be no loss in voltage from the supply to the pin and there's no fear of short-circuiting the power supply.


texts: PIR sensor project (LHI778) with Arduino Nano - sensor doesn't react

texts: When I give voltage to the circuit, the LED lights, but the sensor doesn't work. What  should I change in the circuit?


texts: Why can a MCU input floating pin easily change state?

texts:
I would like a technical ("engineering") explanation of why a MCU input floating pin can easily change its state depending on the outside electromagnetic interference.
Is it related to the fact that the pin is in a high impedance state? If so, how exactly?


texts: How to analyze this circuit in the time and frequency domain?

texts:
I came across this circuit in another post and started looking at the op amp filter  and how to apply traditional circuit analysis ( using 1/jwc for capacitors) and couldn't derive the transfer function.

Question: How would we derive the transfer function for the filter topology? Ignore the HP Filter on the V+ terminal and ignore the components beyond (and including) the zener diode. Use the Generic names, C1, R1, etc.

assume Vin = V+ and we want to find Vo = output of OpAmp.


texts: RISC-V: building a datapath for conditional Branch instructions

texts:
I am simulating a multi-cycle 32bit RISC-V CPU in Logisim-Evolution and so far so good, i had implemented almost every instruction from the basic RV32I ISA. But im having trouble to understand how the condition branch instructions works.

I want to implement:

Branch if equal (BEQ)
Branch if not equal (BNE)
Branch if less than (BLE)
Branch if greater than equal (BGE)
Branch if less then unsigned (BLTU)
Branch if greater then equal unsigned (BGEU)

I have read that the ALU uses 4 bits as input:

3bits: Funct3 or ADD or SUB with with check for zero

1bit: 6th bit from funct7

So than how (or where) is the branch generated? The ALU unit has a ZERO output, and its anded with a control line to activate the branch. But the Branch instructions have all different Funct3 codes, so that means it must be somewhere decoded.

And even than, where is the calculation performed, for example for BGE/BGEU?
We can calculate the BEQ just by subtracting the two numbers in ALU, but what for the others?

My simulation of the CPU for ilustartion

Thanks for any help.


texts:
I'm working on an constant current led driver, in particular the TPS92512 from T.I.

There's audible noise when PWM dimming.

I think that the problem is on the inductor, but I don't know how to solve it, I mean, do I have to pick an inductor with higher DCR, higher Isat, or what?

Here is the LED driver. I changed the inductor to SRR0805-150M.


texts: How is it possible to achieve this functionality?

texts:
I want to control two units 0-10V control inputs simultaneously and inverted way.
For instance if the unit1 input is 5V the unit2 output will be OFF(zero V) and vice versa.

I could do this with using a comparator and its inverting input but there is one more condition I need to achieve. I want to set the outputs to a same voltage value as well.

Basically I want to simultaneously set both units outputs by a potentiometer(any voltage between zero to 10V) but still their outputs will remain inverted(when uni1 is ON unit2 is OFF vice versa). How can this be achieved in a way without using microcontroller?

EDIT:

I hope this makes more clear:

-When FunGen is ON unit1 must be ON and unit2 must be OFF

-When FunGen is OFF unit2 must be ON and unit1 must be OFF

-An interface(like I draw with dashed rectangle) must adjust the voltages to unit1 and unit2 same value when any of them receives voltage). The voltage value must be able to  be set from zero to 10V.

Precision is not important down to 5% is fine for me and zero volt can be 0.2V.

Edit 2:

Related to an answer:


texts: How to turn on a optoisolator with a desired resistance

texts:
I am learning electronics so this is learners question. I wired up the LM339N quad voltage comparator (powered using a 5v power supply through a current limiting resistor of 40 ohms)-in a straightforward standard way- like at

http://www.learningaboutelectronics.com/Articles/LM339-quad-voltage-comparator-circuit.php

but for the potential divider I used two 4.7k resistors-not a pot- and I only used one comparator.  I also had an output  LED too.I added the standard 0.1uf capacitor near the power supply. So the circuit worked as it should (for the input voltages to the comparator I used AA batteries that went through a current limiting resistor of 500 ohm into the comparator input) at 1.5 volts or less the LED turned off. At higher input voltages the  LED turned on.

I want to replace the LED with a pc123 optoisolator, so the optoisolator behaves like a switch (just on or off, with a resistance of between 1 and 60 ohms when on, or zero ohms when off)-so what is the circuit to do this?
So when the opto is off there is no resistance .

There maybe other components (im not sure of this) required in addition to the pc123 for answering  this question . I replaced the led with a pc123 optoisolator but smallest resistance I could get (directly from the phototransistor) out of it was between 5k ohms and 6k ohms and I used a 40 ohm resistor for limiting the current into the opto. If its not possible to get between 1-60 ohms , then whats the the best that can be done to control the output resistance?

here is data sheet for the opto

http://www.ges.cz/sheets/p/pc123.pdf

Also, for a different and related circuit, I want to replace the LED with a bc547 transistor  to turn on a 5v relay -so what is the circuit to do this?

I dont need a fancy answer. I want an answer that show clearly how to answer the question using those components in a minimal way.

Come on folks, try and answer the question!


texts:
I believe that I am fundamentally missing something when looking at schematics. The image below which was used to teach me voltage dividers illustrates my area of confusion.

I understand that ground is used as a reference for the voltage divider, and that each successive point above ground is how much voltage is dropped across the circuit. (So with a 15 volt input, and 5K ohm for each resistor the taps would be 5, 10, and 15 volts respectively.) What I do not understand is by placing ground at that location, wouldn't you immediately sink all the current to ground and have nothing moving through the voltage divider? As I understand it, current will move to either ground or a more positively charged location (such as the positive side of a battery in this case), but with ground located where it is I do not understand why all current would not immediately sink to ground vice the voltage divider. Please let me know if this is just a poorly developed example or where my misunderstanding is.


texts: STM32F042K6U6 BOOT0 pin? Can not understand how to program it with DFU mode

texts:
I'm planning out a board and trying to make sure of how to go into DFU mode and the actual program on a STM32F042K6U6. I want to use the K6U6 for the small size, which also rules out using STLINK to program it (I don't want to use the board space to connect the header).

I've used the K6T6 variant before which has a dedicated BOOT0 pin which I pull low to run my program.

The K6U6 doesn't appear to have a dedicated BOOT0 pin, but, if I'm reading the datasheet correctly, apparently PB8 or PF11 can be configured as BOOT0. But I don't see how.

I'm using ST's CubeIDE btw.

Thanks


texts: Why is the voltage wave magnitude constant along a transmission line that is perfectly matched to a load?

texts: I think I understand reflected waves and standing waves on transmission lines, but why is a traveling wave voltage magnitude constant on a perfectly matched  transmission line? Why doesn't have peaks? I would expect to a decrease to zero in between peaks racing by what ever point is probed, dependent about the phase velocity. I get that there isn't a reflected wave for a perfect match.


texts:
On almost every remote controller the buttons stop reacting after a while, and you end up squeezing the remote out of his life while trying to switch the channel...

I found some link where it explains how to "refresh" the contact-making surface on the backside of the buttons, but that kit is not something I can find around. Could you suggest what would be a good replacement?


texts: Reset 555 timer when trigger switch is released

texts:
I have a simple 5 second Monostable 555 Timer circuit. Trigger Pin (#2) is connected to a momentary push switch. When it is pressed, the timer is started and LED stays on for 5 seconds.

What I want is that if the tactile switch is released during those 5 seconds, the timer should reset. I know, I need to ground PIN # 4 but how to do that when the switch is released?


texts: connecting Wheatstone bridge to pin 3 of LM324 changes voltage?

texts:
Built a Wheatstone bridge with two 10k resistors, one 5k rheostat, and a thermistor.
Adjusted rheostat so that voltage across bridge reads < 0.013v, close enough.

Powered LM324N, pin 4 to 6.07v, pin 11 to 0v (just one 6v battery supply)

When I connect pin 3 of the LM324 (Vin1+) the voltage of that leg of the Wheatstone bridge changes to 5.4v.  I assumed I had blown the opamp previously, and tried a fresh one.  Same result.  So I simplified the circuit.  The only connection to the Wheatstone bridge is a single wire that goes to pin 3 of the op amp.  Nothing else is attached, and yet connecting that wire changes the voltage between the two resistors to 5.4v.  When I disconnect, they go back to 3.03v as they should be.

Here's a picture of the breadboard in case I am just out of my mind.  I can't believe power is leaking out of the input of an LM324, I must be doing something boneheaded but can't see it.
Picture attached.  The perspective isn't 100% ideal, but the wire from the Wheatstone bridge is connected to pin 3, and pin 4 is Vcc.

This was my attempt to simplify the original problem.  I built a differential amplifier to amplify the output of the Wheatstone bridge, and current was leaking out of both positive inputs back into the bridge.  So I wanted to isolate the problem.  I don't have a picture of the board implemented that way, but here's the schematic:

R1 was 10k, Rgain was 1k, R2 and R3 were all 1k


texts:
Following on my unanswered question about bluetooth noise, I have now believe that I have learned a bit more about my problem.

I have built a Arduino controlled circuit to replace the pots and switches on an electric guitar. You can find full information at the webpage.

I communicate via Serial Port Protocol. A bluetooth module is connected via shielded cables to the circuit board.

The audio part of the circuit is fully opto-isolated from the command part.

At each data exchange, I can hear a faint click out of the amp.

After quite some searching, it seems that this click is a result of radiation from the 5v square waves passing along the rx and tx wires, despite the shielding.

I further shielded the cable with a copper mesh sheath, and this reduced the click intensity. As did wrapping the connectors in tin-foil.

I am wondering:

Why/how the shielded wire lets the EMI radiation out?
If changing to 3v square waves would further reduce the intensity of the click?
Why there are no clicks when using a USB cable to communicate instead of the rx/tx?
If there is any way of preventing this EMI from being radiated?

Here is my best attempt at showing the physical layout.  Note that the cable to the BT module is now shielded.


texts: Alternation of Magnet Poles in DC and AC Generators

texts:
I want to create a generator. The current design I am looking at has several magnets along a wheel, with coils around the outside of the wheel. The wheel then spins generating current.

I know that if I alternate the poles of the magnets, I will be generating AC Current.

So my question is, If instead of alternating the poles of the magnets, If I have all the same poles facing out, while I then be generating DC pulses instead of AC?


texts: I want to increase the speed of my 12v DC trolling motor

texts:
This has been a project I have wanted to do for some time now. I live on a large lake  where gas engines are not allowed. I love to fish, but some of the best spots are a long boat ride from home going only 5 miles per hour. What would be the safest and more reliable way to increase the speed of the motor using the existing components?
the "MINI KOTA endura 44" is the only "EXTRA" motor I'm willing to experiment with.
I don't know if it might help answer some of the questions, but I found the manual online:
https://minnkotamotors.johnsonoutdoors.com/sites/johnsonoutdoors-store/files/assets/misc/MI/M/MIN_productmanual_EnduraC2-45/MIN_productmanual_EnduraC2-45.pdf?_ga=2.248790979.515972356.1601483274-397649940.1601483274.
I have started learning about voltage multiplier circuits, maybe increasing the diameter of the wire windings?
I would appreciate some input because this has been drilling a hole in my brain!


texts: Is it safe to go over a fuse holder voltage rating?

texts:
I am looking to buy a few online fuses and fuse holders for the mains power into a kiln I’m fixing up that runs on 240V and draws 45A. A thick 6 AWG wire connects to mains power, then is split into two 10 AWG wires in parallel per hot line. This is to connect to a terminal block with smaller connectors. This is how the manufacturer wired it, not me. If one of the 10AWG wires was to be disconnected, the full load would be pushed through just one 10AWG wire, which it cannot handle, even though it would not trip a breaker.

As a safety feature I want to add fuses to each of these smaller wires. Here is a simple diagram of how I would add them.  I found this fuse holder to be suitable for my application. It has a voltage rating of 32V, but the fuse I’m using in it is rated at 300V or higher. I can’t see any problems with using this holder since it appears to be thoroughly electrically insulated and there will be no arcing at that voltage. Here’s a picture of the holder in case the listing is ever taken down. Are there any other concerns I need to consider?


texts:
I know that this might seem like a stupid question, because declarative is not really an electrical term. I'm having a discussion (argument) with someone who is a functional programming fanatic, and they claimed that

Nope, they're fundamentally declarative. They built an imperative instruction set on top of a declarative model. ISA and machine code is imperative, sure. But; CPUs, GPUs, etc are all declarative.
If it wasn't for diodes, all parts could be emulated in lambda calc. Hence why it is a bicartesian closed category.

I disagree with this, because I would argue that CPUs are machines that have internal state that they mutate. In fact, computation is all about mutation (of memory, or registers, or latches).
Who is right?


texts: Transfer function and characteristic equation

texts:
I have the following network (page 805, example 14.5, Agarwal & Lang, Foundations of Analog and Digital Circuits):

The associated transfer function for \$i_z, v_z\$ is \$ H(s) = \frac{I_z (s)}{V_z (s)} = \frac{s^2 + (R/L) s + 1/(LC)}{s/C + R/(LC)}\$. I can see how to get this from the impedance model of the circuit.
The example says that the numerator of this transfer function is the characteristic equation. The textbook example concludes that "the roots of the characteristic equation [numerator of transfer function] are complex and therefore the circuit is resonant", brackets comment mine.
I'm a bit confused by this since I thought that generally the characteristic equation is the denominator of the transfer function.
I think that the denominator of the transfer function is the characteristic equation of the output variable, so if you took the reciprocal of this transfer function, then \$s^2 + (R/L) s + 1/(LC)\$ would become the denominator and would be the characteristic equation of the new output variable \$v_z\$, so then you could analyze \$s^2 + (R/L) s + 1/(LC)\$ to find that voltage's oscillation frequency \$\omega_0\$, damping frequency \$\alpha \$, quality factor Q, etc. However, these would not directly correspond to \$i_z\$ or the magnitude/phase plots of the original transfer function \$ H(s) \$. Is this correct?


texts: A question about controlling pm DC motor with long signal wires

texts: I have a PWM driver board for a 12V pm DC motor(like toy motors) to control its speed. To create a shake effect the motor will be mounted 50 meters far away from the PWM driver board, for such long wiring is there any extra practice for such application?


texts: Options for solar rechargeable battery powering LEDs?

texts:
As part of my practice I make paintings and drawings with embedded LEDs controlled by an Arduino clone and LED driver. I showed 10 new pieces during an exhibit recently and had great feedback but there were a few of the inevitable comments about "the wire" (i.e. the wire to the wall wart transformer).

I'd love to lose "the wire" and power these through some combination of solar panel and rechargeable battery. I'm no electrical engineer but the bit of research I've done leads me to believe that this is no trivial technical task. Combine that with the fact that most installations of work like this in the home (office, restaurant, etc) would not be in an area getting full sun and that even if it were possible, hanging work in direct sun has a harmful effect on it. And then there is the additional cost, whatever that might be.

So...before I conclude that it is not viable (technically, economically) I thought I would ask for more informed opinions. Spec-wise, in these current versions, there are 64 LEDs (average 2.3-3.3v), an Arduino running at 5v and a Maxim7219 running at 5v. No realtime clock to sleep the piece.

Would it even be possible to charge solar cells/recharge a battery under typical indoor, non-direct sunlight lighting conditions?


texts: Software for computing AC resistance in a transformer - Proximity and Skin effect - Dowell Equations

texts:
I'm looking for a software which can compute the losses (or just the AC resistance of the wires) in a transformer due to proximity and skin effect in function of the different parameters of a transformer (number of layers, core size, interleaved or not, current waveform applied to the transformer, etc). It would be nice if it is based on the Dowell's equations or even better as the Dowell's equation are based on sinusoidal waveform current.

Otherwise, is there someone who knows the equivalent equations of the Dowell's equations for a SMPS waveform ?

Thank you very much,


texts: the voltage output and resistance of a potato

texts:
For an undergrad lab experiment on noise analysis in various electric power suppliers, I constructed a battery from a potato with Cu/Zn electrodes and measured the outgoing voltage. Now I want an academic reference for the expected voltage from a potato and its resistance.

Is anyone familiar with something like this? I could only find this paper but I didnt apply any external resistance on the potato so I'm not sure it is suitable for me.


texts: Absolute minimum delay required to process data across shift registers

texts:
In an effort to make my serial data processing faster, I attempted to use serial mode 0 with a system clock speed of about 3.686Mhz. Its clock comes from the ALE output of an unprogrammed at89S52 that has a 22.1184Mhz clock attached to it.

Rather than resort to bit-banging, I'm going to try to lower my crystal speed because I was looking at a datasheet for 74HC595 from Texas Instruments and it mentioned about some rise and fall time for 500ns and based on 8051 documentation serial mode 0 makes a clock at 307200Hz (1/12th the 3.6Mhz). I also seen values of 100ns and numbers close to it in both 74HC138 and 74HC595 datasheet as well.

Basically the circuits I show is pretty much a serial to parallel data expander in which the output dataset is selectable by the microcontroller, and also the microcontroller can issue a flush to the registers when its time to display the data.

What's the highest speed crystal I should be using for this microcontroller to overcome the propogation delays under the worst-case scenarios (assuming power is 5VDC regulated)?

Do I just add the biggest delays up for each bit or is it more involved?

And when I send the data, I'll be filling all the bits up. Example: for device zero, I'll be filling up all 16-bits and for device 1, I'll be filling up all 24-bits, so the clear functionality of each register is unnecessary as the outputs will eventually be connected to LED's through resistors anyway.


texts:
When the loop is the figure shown below will be rotated in clockwise direction the the slip ring connected to the red segment of the loop will give us the positive voltage and the slip ring connected to the black segment of the loop will give us negative voltage according to the Flemings right hand rule.

What if the loop is rotated in counter clockwise direction ? Will the slip rings provide us the same polarities which they were giving when the loop was moving clockwise ?

Plus

The voltage from the loop is given by the equation.

V(t) = Vmaximum * sin (theta)

Where theta is the positive angle the red segment makes in the clockwise direction or in counter clockwise direction from this position ?


texts: What is causing a voltage drop on the 5v power rail on this bench setup?

texts:
I am testing a video card and because I need to probe the logic chips on the 5V circuit I thought about hooking it up to my bench PSU. I am powering and measuring on the ISA pins where 5V and GND are exposed.
The card has convenient headers for those

So bench supply is connected to B1 (GND) and B3 (+5v)
Multimeter is checking voltage on B31 (GND) and B29 (+5v)

What I noticed was that I am seeing a very low voltage on the power rail when it is powered like that.
(I did the same with another videocard and I had the same readings).So that makes me think the issue is not related to the videocard itself. The PSU keeps saying 5.08V, so I don't see the voltage drop there. But I am seeing it with my multimeter.

When attached to a computer, that voltage drop on the power rail is not there, as it keeps outputting a clean 5V wen measuring with the same multimeter.

Why exactly is causing this on the bench setup ? I know that when something is shorting that I typically see it on the bench PSU (the voltage drops to almost zero). Here this is not the case as it remains on 5.08V and sees a steady current. Bot when measuring I only get 3.1v, meaning that all the logic chips also only get 3.1v so not really representative as a test.


texts: Schmitt trigger oscillators interfere with eachother (74HC14)

texts:
I am using a single 74HC14 (hex schmitt trigger) to implement three oscillators. I now have a test build ready and encounter problems. See schematic, it shows component values. Also

proper 5V power supply
2u2 electrolytic bypass near chip
100n ceramic disc bypass next to chip
unused schmitt triggers' inputs are on ground or vcc
outputs connected to inverting opamp amplifiers, each their own opamp with 100k and 500nF in series to the inverting input (the C is for DC blocking)

The problem is: each of the three oscillators interfere with the other ones, changing their frequency. E.g. if oscillator 1 is set at 50 Hz, turning up 2 or 3 will cause 1 to go up in frequency (wild changes, think +50%)

I'd think the schmitt triggers are not loaded very high (resistances are all >100k, problems occur with the potmeters at around 200k already) so surely I'm not pushing it in terms of sink/source current.


texts: Don't know exactly where I should post this but I'm pretty sure it would be fine here . I was walking home right now late a t night and I walked by this persons house and out of no where I heard a click and a really high pitched sound that made my ears ring suddenly came on then I kept walking and what I assume was the end of his house another time that high pitched sound came on . Is this a motion sensor of sorts or am I going nuts? I didn't walk back to see or try it again cuz it creeped me out I was wondering if  there was motion sensors like this or is it something else. Thanks for reading.


texts: How does this non-isolated circuit create 12VDC from mains supply?

texts:
I took apart a PIR sensor, and inside it has a circuit similar to this (it uses the same chip):

I don't quite understand how this rectifies and creates 12VDC. My understanding so far is the (68 + jw0.68) is the current limiter, and the 12V zener is used as a reference voltage.

However, I'm having understanding:

The ground point (i.e. the wire between the two zener diodes) and polarities. On the positive cycle, the top zener will be ~12V, and the bottom will be ~-0.7V, referred to the ground. In the negative cycle, the opposite will occur. So how does this rectify the voltage?
How does the 470uF capacitor act as a smoothing capacitor?

I simulated the circuit like so:

As you can see, the top oscillates between -0.7mV and 12V. Why is this node connected to anything if it isn't 12V?
I'm not sure why it becomes a square wave, but that might be another question.

I'm not sure if I connected the load in the correct place. It's only drawing 7.5mA and cannot regulate the voltage at all..


texts: Reverse engineering LCD signals on HP power supply

texts:
I have recently acquired an HP 6632A power supply and was inspired by Roberto Barrios' project of replacing the screen with an OLED display to do the same. However, it is evident that the 6632A is much different as it doesn't have a front panel board and separate serial connection. Instead, the LCD driver is controlled directly by the CPU through a latch.

Pg.101 of the service manual

Looking up DFI, ISA, SYNC, INA, etc yielded nothing in combination with LCDs.

Picture of the LCD board:

I probed up the 16-pin connection according on the schematic, though I could be missing something.

Signals when "VSET  0" is displayed:

These signals are sent at ~2.5Hz when idling:

Here are the rest of my captures

I'm not sure where to go from here. Probe 6 looks like clock (hooked up to pin 12 on the left), yet it stops when data comes in. Probes 4 and 5 appear to be exactly the same, just shifted 5us. I'm not able to get any sort of serial decoding working through Saleae Logic, obviously. I probed the rest of the pins to make sure I wasn't missing any signals (or negative voltage for the LCD). I've tried to compare the enabled segments' binary representation with the signals, but I couldn't make any correlations.

I would appreciate if someone could point me in the right direction. Thanks!


texts: Current flow in a simple flyback topology

texts:
I'm continuing my learning about flyback converters, and trying to understand the current flow and the magnetic fields involved.

For instance when the mosfet is on current will flow through the primary winding, but since the current flow in the secondary would be reverse biased no current flows into the capacitor (or from the capacitor back into the secondary).  Current may flow out to the load at this point from the cap.

Now what I don't quite understand fully is what happens when the fet is turned off?  I think the magnetic field will start to collapse and that this will result in current flowing in the other direction as the field collapses so now the diode will be forward biased and current will flow in the secondary loop.

But what happens on the primary side?  Does the current flow through the body diode of the FET on the primary side?  Or does the field somehow just collapse and pass it's energy onto the secondary with no need for any current flow in the primary. I seem to remember that's the point of the body diode when switching an inductive load but I'm not sure.

Edit

After watching the video in the comments it gets to a point where it shows the current flowing in the opposite direction but he's just modeling it.  So what he calls the magnetizing inductor isn't a real part.   So what's providing the loop for the current to flow on the primary side?


texts:
I have an application where I need a 24V DC Power source at approximately 5 Amps (so approx 120 Watts).  I've also got a shed load of old computers which all have 12V power supplies rated at up to 300W.  Is it safe/okay to connect two ATX power-supplies in series to achieve what I'd like to do (which is a 24V DC Power Supply on the cheap).

Thanks in Advance, Patrick


texts:
I was experimenting with logic gates on my breadboard and tried a 3-input logic gate.

I got the following result:

Input  |  Output
A B C  |   ?
0 0 0  |   1
0 0 1  |   0
0 1 0  |   1
0 1 1  |   0
1 0 0  |   1
1 0 1  |   0
1 1 0  |   1
1 1 1  |   1

What logic gate could this be? Thanks


texts: does 0,7V supply on 5V devices damage the device?

texts: In a certain state of my circuit there will be 0,7V on the supply pins of certain IC's (comparator & current sensor). Of course the IC's won't work on this voltage but does this damage the IC's or can I ignore it? The voltage is caused by a diode (it's leaking some current probably) & a dc-dc converter.


texts: Why are these batteries I bought from Costco called "Battery Piles"?

texts:
This might not be the right stack exchange for this, but I bought a pack of generic 48 alkaline AA batteries, Costco brand (they're probably manufactured by Duracell since that's the only other brand Costco seemed to carry), and they called them "Battery Piles." I know that one of the first voltage sources, by Alessandro Volta, was called a voltaic pile, but I was under the impression that modern batteries use a different chemical mechanism for power delivery, and my research into this topic seems to back this up.

So why are these batteries called "Battery Piles"? Is this a marketer's attempt to avoid IP infringement, or is there a new mechanism that they use for batteries?


texts: Op-amp voltage boost circuit : how does it work?

texts:
I want to boost the output voltage of op amp to a higher value.
I found the conceptual circuit below online.
I understand that Q1 and Q2 are used to provide the necessary supply voltage for the op-amp.

link : https://www.analog.com/media/en/technical-documentation/application-notes/28080533AN106.pdf
figure 14

But how do the other parts work ?
In particular, the voltage gain is apparently Av=3 (written in the text).
How did they arrive at that?
Should the (voltage gain)Av not be -33 ?

What is the function of R4 and R3?

EDIT:
In the answer by Photon, it is stated that the gain of the whole circuit is 33 while the gain of the output is 3 .
So you can have 2 gains in an op-amp ?
So one is the gain of the input to the Vout? and  the other is the gain of the op-amp output to the actual Vout?(the second one is bit confusing)


texts: Why am I getting no gain from this differential circuit?

texts:
I am having difficulty understanding why I am getting unity gain from the circuit below. Before I added the common emitter stage, there was a gain of around 150, and I wanted to add another 10 X gain to that, but as soon as the CE part was connected that gain went to around -1.

Looking at the probes, it seems to me that everything is in order: 1/10th current at CE transistor base, mid point DC bias at output.. shouldn't the ratio of collector and emitter resistors give at least 8 X gain?

I've studied separate components of these amplifiers in textbook format, but getting stages to work together in a practical application is, unfortunately, beyond me for now.

Thanks for any help you can give.


texts: Can I see all part properties in LTspice?

texts:
I'm a beginner at using LTspice, and I want to see all the part properties in one slide.
Like this:
R1 : 10k
M1 : W= 10u, L=10u ....
M2 : W= 50u, L=10u ....
How can I do this?


texts:
I am trying to understand working of MPPT charger for LiPo battery (3.7V nominal) and 6V 2W solar panel so that I can select right charger for my project.
After searching and reading lot of related material on the net, my understanding is that, while charging, in all light conditions, the voltage from solar panel will remain more or less  constant, but the available current will change.Thus at the Input side of charger we are getting more or less same voltage but varying current as the light changes.
 At the output side of charger, voltage must be higher than the battery voltage (to be able to charge it). Thus charger will keep on monitoring battery voltage and keep the output voltage higher than that.
But as the light condition changes, the available current from the panel changes, and so does the MPP (maximum power point), and the charger adjust the out put voltage to the MPP voltage (to get most of available power for charging). But still this voltage will be higher than the battery voltage.
Please correct me if I am wrong.


texts: How to get complex reflection coefficients?

texts:
If I terminate a line with an open circuit, I'll get reflections of any incoming signals with the same phase (a reflection coefficient of 1). If I terminate the line with a short circuit, I'll get reflections of any incoming signals with opposite phase (a reflection coefficient of -1).

What can I terminate the line with to get reflections with different phases, i.e. complex reflection coefficients with magnitude 1?


texts: How to wire ATMega32U4 Hardware Serial to Arduino Mega2560?

texts:
I’m designing a custom, Arduino Mega2560 based, PCB for my project. One of its job is to run a bipolar stepper motor via a TMC driver amongst many other things.
From what I know, the AccelStepper library works by sending a pulse whether it’s due for one in the run() command. Because of the other parts of the codes taking up time in the loop, my max step speed would be a lot lower than the 4000 steps/sec the Mega would be able to do.
One workaround I’m thinking is adding a dedicated ATMega32U4 (Arduino Micro) just for running the stepper so it can maintain the 3000-4000 steps/sec. The Mega will communicate with the 32U4 via hardware serial (baud rate set at 115200) to update the stepper motor’s motion.
Here is the tricky part; the 32U4 only have one hardware serial port (pin 0 and 1) but it’s also tied to the USB interface. Since D+ and D- pin is connected to the USB data pin, does that mean pin 0 and pin 1 is also tied to D+ and D- pin? This confuses me in how I should wire the pins.
I was thinking of a slide toggle switch to switch between the 32U4 being connected to a USB port or being connected the hardware serial port of the Mega uC chip. My thinking is I’d use the USB port to upload the sketch. Then I’d use the slide switch to break USB port line and reroute it to the Mega as it waits for commands. Do I break the D+/D- line or the D0/D1 or both?


texts: Can two electrolytic capacitors be made into a bipolar?

texts: I know if you put an electrolytic capacitor backwards they explode and it's quite fun to observe them exploding. I am wondering if you can use two of them (and some diodes) to turn it into a bipolar capacitor so it may be used with AC signals?


texts: Why do 16 bit systems have a minimum dBFS of -96?

texts:
I'm working through the example on this page:
http://chimera.labs.oreilly.com/books/1234000001552/ch03.html

I totally understand why the maximum level of an audio system would be 0 because the log of 1 is 0.

However, I'm confused about the minimum. The definition of dBFS is

dBFS = 20 * log( [sample level] / [max level] )

In a 16 bit system there are 2^16 = 65536 values. So this means values from -32768 to +32767. Excluding 0, let's say the minimum value is 1. So plugging this into the formula gives:

dBFS = 20 * log( 1 / 32767 ) = -90.3

But the book is saying it should be -96dBFS. Where am I going wrong?


texts: Designing a safe Amplifier to drive Sound Card Mic Input

texts:
I've designed an amplifier to receive ELF-VLF (3hz to 30Khz) signals through a loop antenna and want to connect it to Sound Card mic input to analyze received signal.

The problem is that the maximum output of the circuit sould be limited to protect sound card from damages and avoid cutoffs in waveform because of saturation to prevent data loss.

I'm going to use Mic input over laptop and it should not be confused with Line In.

What is the maximum and nominal voltage values for microphone input? How much is the input impedance of Mic jack?

**Edit: ** It's going to be introduced to a group of enthusiast people with limited knowledge about electronics and it's definitely NOT a precise solution but a cheap and easy-to-use one. The aim is to keep it simple and safe. So please do not think of limited frequency response of sound cards or the exact maximum voltage suitable for every specific card. Just a safe voltage range should be enough.


texts: When would a design need multiple batteries?

texts:
In general it seems that using only one battery (pack) in a system design is a good idea, as it reduces complexity and cost.  One configuration of series/parallel cells rather than multiple configurations to manage.  Are there typical exceptions where using a second battery, or even many batteries, is considered standard practice?

I can think of a few cases:

Enable fail-over to backup battery in case main battery fails or runs empty, giving people time to swap or charge the main battery before the system goes offline.  May also enable hot-swap of main battery without powering down the system, e.g. laptop computer, albeit hot swap could simply require wall power.

Make use of a secondary bay to increase battery runtime as an optional feature, e.g. swap DVD drive for second battery in laptop computer.

Are there other good reasons to have a second battery in a system?

For example, Does an all-electric vehicle (e.g. Tesla) typically have a second, smaller battery for powering safety-critical electronics?  Is the battery bank in a solar array typically one large battery or a collection of modular parallel batteries?  Any other places multiple batteries would be considered ordinary?


texts:
I use Atmel ARM chips and I'm used to use Atmel Studio 7 for developing. I want to try a more elegant editor for developing and I like the Visual Studio Code (VSCode). It's very nice editor. But I don't know how to use it with ARM toolchain which Atmel Studio has.

Any hint about how I could get started with this?


texts: How do you design a bridge rectifier circuit?

texts: I am trying to design a bridge rectifier circuit (without capacitor). When I try measuring and graphing the output and input, the input looks fine but the output is just a straight line. Did I design the circuit wrong? Or am I probing the wrong spot?


texts:
When trying to program a project in MPLAB X IDE using the PICkit 3 programmer, it fails as MPLAB X shows this error:

I have connected the PICkit3 with USB.
I'm using OS X 10.9 and the latest version of MPLAB X.

Hovering over the PICkit3 option in the tool selector shows this:


texts: Constant current led drivers shared ground

texts:
I have 4 constant current led drivers with PWM. Here's 300-1500mA LED Driver datasheet.

I want to use 3 of these drivers to power each color of a 90w rgb led. I was under assumption that I could connect the positive output of the driver to the individual colors of the led and the negative output to the shared negative connector of the led.

What happened when I tried that was a puff of smoke and one destroyed driver (not output voltage). If I connect negative output wire of the driver to individual negative led connectors everything works as expected.

What am I missing here? The main reason I need shared ground is because PWM flickers if arduino that I use for PWM is not on same ground as the led driver.