texts:
I'm building a Stepped Tone Generator (AKA Atari Punk Console (APC)) based circuit, which is not a stand alone device, but which will feed into a number of subsequent stages/circuits.
The majority of the schematics out there show the audio output referenced to GND, like so:

However, I have come across three schematics (1, 2, and 3), which have the sleeve (and ring) of the jack, or speaker (as in the original design by Forrest M. Mimms), connected to the +V line:

The tip/pin of the jack in this case is connected to the +V and the sleeve to the output

The sleeve (and ring, if jumpered) is to +V and pin to the audio output

The speaker, in the original circuit, is connected between the output and +V.

I understand that the DC bias of an audio signal is irrelevant, and is blocked by C3

TL;DR

In the first example, with +V connected to the tip, the effect output is effectively the "right way up", but with a moving ground, as the signal is now the ground, especially if connected to an amplifier (where the amplifier's input sleeve is connected to GND).
In the second example the signal would appear to be inverted, as the ground is now +V.
Why did Forrest M. Mimms not connect the speaker between the output and GND?
Shouldn't the GND line be used, especially if connecting the APC to another piece of grounded audio equipment, such as an amplifier?
Does it make a difference, if +V or GND is used, as the DC bias of the signal is not relevant?
Are there any advantages to doing this (using +V en lieu of GND)?

I am confused, but that could just be due to my conditioning that signals should be referenced to GND. I have never seen (or maybe noticed) this +V referenced type of signal/circuit before. Is this related to virtual-grounding?


texts:
This is a follow/new insight regarding my previous question Messages for SPI protocol.

One idea from that question is to use the SS line to know a new message is being sent from the master to the slave. The master will be the STM32 and the slave the Arduino, see below:

  Slave   <---  Master
 Arduino  (SPI) STM32
   |            ^ ^ ^
   V            | | |
RS485/DMX512   3x UART/MIDI

The Master receives MIDI signals from various sources, processes them, transmits (changed) MIDI messages back and sends SPI messages to the Arduino which sends the DMX signals.

So far so good, I am currently implementing the Arduino code (including a Windows test application).

The reason I use an Arduino for RS485/DMX is mainly because I couldn't get it to work on an STM32, but also to relieve the STM32 processing power.

However, I need more SRAM on the Arduino, so I will use a SPI SRAM chip (32K256). The problem is, that I'm not sure if I can let the Arduino be the slave.

SPI RAM 32K256
    |(SPI)
    V
   Slave   <---  Master
  Arduino  (SPI) STM32
    |            ^ ^ ^
    V            | | |
RS485/DMX512     3x UART/MIDI

Some things I considered:

Making the Arduino the Master, and poll to the STM32 (resulting in my useless poll events likely).
Keeping the STM32 master and when a send fails to retry.
Using I2C but I think SPI is easier to implement.

Afaik the communication needs to be completely synchronous, but I'm not sure if there is some 'relaxation' due to buffers inside the SPI peripherals.

Some more background information about the entire project:

The STM32 read inputs from various MIDI inputs (synthesizers mainly)
At a later stage I might also add other inputs (non MIDI).
The STM32 processes these messages and sends out MIDI messages and commands for the Arduino slave.
The Arduino slave processes the messages which can be something like (make all front DMX lights fade in and out between red and blue, make lights X and Y green, switch on stroboscope with speed 50, etc). These messages all have the same length (18 bytes).
For each DMX light (17 so far, but can increase in future), I have a class (instance) that keeps information (max 64 bytes) per light, this will not fit in an Arduino, so I use external SRAM.
As often as possible (but at least every few ms), the Arduino processes a light, by reading its data from the SRAM, and changing the fade colors, and also processes new commands from the master if there are any. And finally saving back the changed data to SRAM.

Any insights would be helpful.


texts: Why are the 10A inputs on many multimeters unfused?

texts:
Most multimeters have a current measurement setting for low currents where a fuse is present. However, to measure high currents up to 10A, you need to use a second input that is often unfused.

Now, I understand why a second input is needed (the low-current fuse can't support 10A currents, and you definitely don't want a 10A fuse for low-current measurements). But what I do not understand is why the 10A input may not have a second fuse that is either 10A or slightly larger than that.

So, what is the reason for the 10A input often being unfused?

I understand that some high-end multimeters may have a 10A fuse, so is this a cost related issue?


texts:
I've successfully used an Arduino Uno to trigger Halloween props by closing the normally open circuit on an SRD-05VDC-SL-C relay. I am basically replacing a contact switch and tapping into each prop's "try me" circuit as depicted in the following 2.5 minute video:

Link to instructional video

I'm now trying to replicate the functionality on a breadboard by connecting the base leg of a BC337 transistor to a digital output pin on an ATMEGA328P-PU. I can make it work with every prop but as is suggested in the video I have to respect polarity when using the transistor. The relay works with every prop irrespective of polarity. Is there a way for me to make the transistor work irrespective of polarity too?


texts: Operation of simple FM transmitter circuit

texts:
I found the following little FM transmitter circuit among some old papers and it works pretty well, but I have a tough time understanding how the circuit operates:

I understand the trimcap and inductor form a LC tank circuit that resonates at the required frequency. I don't understand how the transistor keeps the tank "topped up". Can anyone explain the circuit's operation in detail ?


texts:
Specifically, I ask about the Molex 36638 series header, but I guess that it is a more common term.
I searched Images for a peg, for a split peg etc. but I still have no idea what it is about. There is no further explanation in the respective datasheet https://www.molex.com/pdm_docs/ps/PS-36638-001-001.pdf.


texts: How to provide symmetrical power supply with laboratory power supply?

texts:
I am making a circuit with operational amplifier. I want to provide symmetrical supply, -12 V and +12 V, because I need differential amplifier, to obtain both positive and negative output voltages.

I wonder, how to provide such supply with laboratory power supply. I have 3 sockets: +, -, and GND. How should I make connections between those sockets to obtain symmetrical supply?


texts: Automotive Load-dumps, ISO standards & Meaning behind datasheet

texts:
Im looking towards using an system basis IC for one of my designs (UJA1164A)
and i noticed that under the features & benefits it notes that

"Battery and CAN bus pins protected against automotive transients
according to ISO 7637-3"

i unfortunately don't have access to the sheet so i'm unaware to how far this standard goes, and wanted a second opinion.
In either a 12v or 24v automotive application how well would it fare (or at all) with a load dump, especially if we're talking about a 24v system that expects around 170v for few hundred ms without a beefy TVS to clamp it ?

worst case i was looking to the TIDA-00992 for additional protection or putting in some big boy tvs suggested on here Link
or one of these tvs tvs link


texts:
I want to design a voltage divider circuit to bias an op amp, this circuit will be a part in another circuit to measure a biomedical signal. Is there a  noise issue arises from using voltage divider to provide biasing? if I choose R1 = 10K and R2 = 10K, then will it make any difference if I choose R1 = 10M and R2 = 10M?  In a paper I read the following:

  Using a simple resistive bias network is impractical from a
  reliability and noise standpoint.Although a biasing resistor can be
  bootstrapped to the required resistance, minimizing its current noise
  contribution requires an impossibly high value

I don't know if they mean a voltage divider by "simple resistive bias network", but I assumed that.


texts: A more elegant solution to wiring this system?

texts:
I have a pressure system with eight solenoid valves on it and I'm controlling it from an Arduino. For each valve I have a solid state relay that an Arduino controls to switch on and off 12V from the supply. I've gotten this circuit to work properly with a single relay and solenoid:

Now I'm beginning to scale it and it all works but my setup is pretty messy. Here is a single SSR hooked up to a single valve and then the holders for all the other SSRs on the board:

So I was planning on using that terminal connector and then that small proto
board mostly because this will be changing around a lot and I may be throwing some more pieces in so I don't want it to be 100% permanent but I do want it to be more durable and a little more elegant. Any thoughts on how I should wire this up? Or anything better than that terminal connector?

Here is a schematic of half of the full setup:


texts: Batteries for solar application, why C10 only?

texts: Some Solar PV system integrators in India are insisting on using C10 batteries only, which they have named solar batteries.  In my view the selection of battery depends on charging source , environmental condition and discharge requirement.  That is why I have posed the question as why we need C10 batteries for Solar, or is it mandatory?


texts: Interpretation of Rotation Vector Measurements

texts:
I use android devices (Xiaomi Mi9-SE (Android 10) & Huawei P10 (Android 9)) to collect movement data from bicycle rides. Hereby, I am measuring i.a the Rotation Vector which describes the rotation of the smartphone to the earth's reference frame (https://developer.android.com/reference/android/hardware/SensorEvent#sensor.type_rotation_vector:).
The sensor returns four values, which represent the rotation as a quaternion (w,x,y,z).
In my experiment I recorded a bike ride with two smartphones, which were glued to each other in the same alignment. When I plot the returned values from the Rotation Sensors numerically, they seem to be similar in some phases and dissimilar in others (cf. 1, 2)
However, when in a dissimilar phase (e.g. ~22:12:30h), it seems like the rotations are still somehow the same, but the axis are swapped. I plotted two corresponding rotations (cf. 3, 4). If the x and y axis were swapped and mirrored on the new y, the rotation would become similar.
I wonder if this behavior is due to inaccurate/bad sensors or whether I missed something working with quaternions.
Would be really great if someone could tell me, if/where I miss a point here.


texts: Generate TTL-level reset pulse from RS-232 level signal

texts:
(My knowledge of analog circuit design is severely limited).

I am trying to generate a reset pulse for an AVR microcontroller. The reset is active LOW, and the maximum threshold voltage is 0.9V, with a pulse of no less than 2.5us.

I am trying to generate the required pulse from the DTS line of an RS232-Level signal. This means that the DTS line voltage is from ~-13V (inactive) to ~+13V (active).

simulate this circuit – Schematic created using CircuitLab

This is the best I could come up with, and it does not work. I have simulated using Spice, and depending on the ramp of the positive edge of the DTR pin, the RESET_N may never go under 2.5v.

The simulation from CircuitLab:

The simulation from NI Multisim:

EDIT: Added Voltage points to the AVR Circuit to clarify that GND is common.


texts:
Sidenote: You may have seen my earlier question. This is a repost I guess but I've done a lot more work trying to analyze the problem. I thought it warranted asking a new question. Sorry if it doesn't :/

So I have a TI TM4C123GXL microcontroller. I'm trying to produce sound using the GPIO pins and a 10bit DAC I made from a resistor ladder.

The Circuit:

Here's what the hardware looks like: http://i.imgur.com/upVLToV.jpg

So my microcontroller is connected to the DAC with the GPIO pins. The board puts a voltage of 3.3V on the pins for a logic high. The DAC output is connected to a small 3.5mm jack component where you can plug in headphones or a speaker w/ an aux cable.

The DAC is an R-2R resistor ladder with the R being a 10k resistor and the 2R being a 20k resistor. They both have tolerances of 1% each. I also have a 0.1 uF capacitor in parallel with the DAC output to smooth out the curves a bit.

I did a ramp up test and a sine wave test with an oscilliscope and the curves came out quite nicely:

Ramp: http://i.imgur.com/ia0vgqh.png
Sine wave: http://i.imgur.com/3p6lpzc.png

PROBLEM 1: Unfortunately when I plug headphones into the jack, the voltage output is choked and the curve becomes super noisy (notice the voltages marked by the cursors):

Ramp: http://i.imgur.com/5pSkX6D.png
Sine wave: http://i.imgur.com/Azl1cOH.png

The Code:

To produce sound I take an array that is essentially a lookup table for a single period of a sine wave. For this project I'm using an array with 1024 values, ranging from 0 to 1023. Using a timer, I send a value from the array to the DAC using a cursor that scrolls through the waveform. The faster the cursor scrolls (i.e. the lower the reload value of the timer), the higher the frequency and the higher the pitch produced.

Using two timers, I scroll through the lookup table with 2 independent cursors. I then add the values using the the formula A + B - AB/1024 and send this value to the DAC. In theory this should send a mixed signal to the DAC that sounds like a chord.

PROBLEM 2: Unfortunately I get a horrible distortion sound: https://soundcloud.com/rutvik-choudhary/dac-output-test-1

Mathematically this is what I expect to see: http://i.imgur.com/im5bXqU.png

In reality, this is what I get:

No headphones: http://i.imgur.com/CJgjdih.png
With headphones (note that the voltage is choked and the signal is noisy): http://i.imgur.com/xzRqeMI.png

Could anyone point me in the right direction as to what exactly my problem is? I'm not really sure what could be causing this problem...


texts: Advice dc motor for 265mm size radial fan blade

texts:
I modeled a fan (link 1 has the image) and used a drone brushless motor (KV720) for this model. My goal is to reach 2500 rpm, but the dc motor drew 10+ amps at 12 volts and 1000 rpm. When I pushed a little harder without noticing it, the smell came and I stopped testing.
I wonder whatever I do, will I draw 20 or 30 amps at 2500 rpm or can I get rid of this problem if I change the dc motor? (My limit goal is 12 -13 amper at 12v)
If yes, How should the characteristics of the dc motor you recommend?
I looked through a car fan manufacturer's catalog. As the fan sizes increased, they used high-torque and large-sized fans. Can I overcome this problem with using a big fan with high torque dc motor? Or whatever I do will I draw extremely high current?
In addition, I want to give an example which is lived. I purchased a car air conditioner fan (mini radial fan pic link2) model from this company and I modeled with the same size propeller and tested it with a brushless motor (drone motor). They drew almost the same currents at the same speed, but the dutycycle of the brushless motor was less than 50% (that is, it was actually quite efficient). So if I use a large dc motor for large fan, can I get more efficiency from a brushless motor(drone motor?
Fan 1 : Link 1:
The propeller has an end-to-end length of 265mm, a height of 50mm and 10 propellers.
https://1drv.ms/u/s!Ao1QAv8AtzQgpB1fKBnXYFNRMM36?e=1WejTT
Fan 2: Link 2:
The dimensions specified with the product I purchased are exactly the same. The only difference is a dc motor.
https://1drv.ms/u/s!Ao1QAv8AtzQgpBzU_0-5Gou8fZUF?e=irFCXB
https://1drv.ms/u/s!Ao1QAv8AtzQgpBuUNWuPZP2CNa0I?e=beODiN
Brushless motor link:
https://www.f1depo.com/urun/sunnysky-x3108s-kv720-fircasiz-motor


texts: How to determine the settling time from a transfer function?

texts:
Given the transfer function \$G(s)=\frac{(1-\frac{s}{3})}{(\frac{s}{0.1}+1)(\frac{s}{100}+1)^2}\cdot 10\$, I would like to calculate the settling time.

From what I've learned, this is a third-order system, and the settling time can be calculated as
\$T_{a}=\frac{3}{\zeta\omega_{n}}\$ (the same as a second-order system correct me if I'm wrong), where \$\omega_n\$ is the natural frequency, \$\zeta\$ is the damping factor.

However, there are no imaginary poles and I'm struggling to really understand the fundamentals. What's the "right" intuition/approach?

The relative bode diagram:

Update: I am also looking for solutions that involve simpler calculation than finding the Laplace inverse.


texts: Why are the heatproof composites used for semiconductor packages never used for coil formers, connectors and switches?

texts:
It is very hard to destroy the material normally used for "plastic" IC and transistor packages with IR or hot air soldering tools, unless you apply a measure of heat that would reliably destroy the semiconductor in it first. From what datasheets say, the material is more akin to polymer concrete than a
common plastic.
It is very easy to destroy the thermoplastic materials used for tactile switches, smd coil formers, and connectors the same way.
If the first material is cheap (which one would assume, given there are very cheap semiconductors, whereas connectors often are not that cheap), why is it not used commonly to make parts in the second group?


texts:
I am experimenting with a mains 230Vac chopper using IGBTs and needed an isolated gate drive circuit. Much searching and head-scratching led me finally to a pulse transformer design as a simple, effective solution. I tried this app note from IR "AN-950 Transformer-Isolated Gate Driver Provides very large duty cycle ratios" as well as this article "High Side MOSFET Gate Drive: The Power of Well Implemented Pulse Transformers" author Fritz Schlunder. Of the two I had great success with the 2nd one, the IR AN-950 design having some limitations at the extremes of duty cycles at the frequency I was wanting to use. In the process of all this I ran into V.us limitations of the pulse transformers I have access to, and despite reading many articles I still dont fully understand what is happening. Hopefully this august community can shed some light. So to the details... see schematic snip below.

A PWM with 3-95% DC is provided as a single-ended input to a TC4420 driver, driving the primary of the 1:1 pulse transformer via a 1u series cap and 10R resistor, with the other end of the primary grounded. The secondary circuit is according to the 2nd referenced article above. The switching frequency has to be below 50kHz, the limit of the IGBT if I want to get collector currents above 10A. I am using a Murata 78615/8C 1:1 pulse transformer (only one I can get ready access to) and driving with a 10V primary signal. So my understanding is that at 50kHz (20us) I need a V.us spec of 200 for the pulse transformer. However the spec for the Murata part is only 15V.us.
I found that this transformer works well from about 53kHz up. Below 53kHz it begins to saturate and the driver and transformer start overheating. Worst case is at 50% duty cycle, the waveform starts looking like below.

I can bring it out of saturation by lowering the drive voltage, illustrating the V.us relationship.
At a spec of 15Vus and 10V drive the limit should be 1.5us for this transformer, not so? Equivalent to 660kHz, way above my observed frequency. At 53kHz and 10V the V.us figure is approximately 190. So why is this? Clearly I am missing or misinterpreting something?

Your insight and comment would be much appreciated.

Edit: my question does not come through clearly enough, and the waveform pic seems to be confusing as it is not actual but an illustration of a waveform for a saturated transformer, similar to what I had observed. I will grab some actual waveforms and add them to this post.

To be clear about my question: Am I correct in calculating the observed V.us as 190 and if so then why does the transformer exhibit a V.us of 190 when it has a rating of 15.


texts: I have tried to look online but I have no idea what this is so its like spotting a needle in a haystack. It would be really helpful if someone could tell me what this is (see pic). It has a "silver oval shaped blob" inside of it...Also are there any general voltage specs I should know about before connecting it to a breadboard circuit because no specifications were included...


texts:
I want to design an input stage for my DIY midi-drum-trigger.

Piezo-Elements are used as drum trigger and i want to read out the voltage spikes with the built-in ADC of a ATMega168p in order to generate MIDI-Signals.
I checked different resources for how to design a input stage for the piezos, since they generate a very high voltage, but the circuits i found are very different.

Here is a circuit i found at edrum.info:

I am very new to electronics, but this is how i would explain the circuit:
The potentiometer acts as a voltage divider and scales down the signal. The BAT85-Diode removes the negative portion of the signal. I don't know what the resistor in parallel to the BAT85-Diode is good for.
At the output of the opamp, there is a peak-detector circuit to hold the signal-peaks for a specific time and the whole signal is amplified by two (non-inverting-amplifier).
Please correct me if i'm wrong.

In this video is explained, that you should add another opamp acting as a buffer behind the peak-detector-circuit: https://www.youtube.com/watch?v=jllsqRWhjGM&t=10m31s

So here are my questions:

Do i have to add a buffer behind the peak-detector circuit when working with piezos or can i connect the peak-detector-output directly to the ADC?
And if i have to add a buffer: I want to multiplex many piezo-signals with a HCT4051. It is possible to add one buffer at the output of the HCT4051 or do i have to buffer every eight signals before they go in to the Multiplexer ?
I want to drive the opamps (LM324N) from 0 to 5V, and not from 0 to 8V like the circuit above. Is there anything i should change, when using this circuit ?

Thank you !


texts:
The drawing seems to present an electric interlock system. But how the NO and NC relays being energized?
The diagonal with a box should represent fuse, but the drawing doesn't seem so?
BCT should be bushing current transformer but why it is being used here?
Didn't find anything with BCO anywhere!
Having difficulty in linking up all the things in the drawing.


texts: Will two op-amps connected to the same input affect each other?

texts:
I've been given the following circuit to build for an education lab. The values of the resistors aren't accurate; they're only to illustrate that the gains of the two op-amps are different.

The aim is to have two separate op-amps of different gains connected to the same input signals, and then a SPDT switch connects the required output to \$V_{out}\$. The two op-amps will be in the same chip (LM353).

Since the output of AMP1 is fed back, and in some sense is connected to Node2, will the first op-amp effect the gain of the second op-amp and vice-versa? Or will the two op-amps behave as if they are separate and just happen to have the same input signals?

simulate this circuit – Schematic created using CircuitLab

EDIT:
Thank you for the replies. The input will be provided from a MPX2100 thin film pressure sensor which the datasheet indicates should have an output impedance of 1400-3000\$\Omega\$. Is this too large?

If so, perhaps it would be smarter to switch the inputs, or use a buffer op-amp like an instrumentation amplifier? The problem is the PCBs for the circuit were made long ago, and I'm now trying to reverse engineer the circuit from effectively no documentation. So making changes is difficult.


texts: Determining the voltage labeled Vx by Nodal Analysis [Voltage Controlled Current Source]

texts:
How to find the voltage labeled v(x) by Nodal Analysis?

The sum of currents from node 2 to node 0 is equal to 0. However, I do not know the the current of 0.1Vx. How to solve the question?

Thank you for your help.


texts: Power Dissipation - Sizing up Power Supply Needed

texts: I wanted to understand what size power supply is needed for the following: I am getting confused with the Icc value and Ioh,Iol etc values in the datasheet. My question is, how much current will I need to supply to U1 device assuming the values I have here. Even though Icc=500uA is in the datasheet as max, won't the IOH value add to this number? I am assuming frequency is low and input capacitance is low for this example.


texts:
I am trying to determine the necessary power supply specs/requirements for a set up I've been working on. Doing some background research on the subject of course brings one to the Power Equation (P=I*V).

I already have the rated voltage and amperage requirements for most of my components. An example list goes as follows:

Motor 1 - 30V, 4 Amps
Motor 2 - 30V, 4 Amps
Peripheral 1 - 30V, 2 Amps
Peripheral 2 - 30V, 2 Amps
Peripheral 3 - 30V, 2 Amps
Controller Board - 5V, .5 Amps

Based on the examples I have seen, one performs the power equation on each item and then these can be individually summed up, which gives me a total of 422.5 Watts.

My first question, is this the correct procedure ?

Second, in addition to the watt rating of the power supply I also see power supplies have a 'max current out' rating... How does this figure relate to the power calculation above ? Or I can understand I need a power supply that is rated at least 422.5, but is the required max amperage out dependent on the highest single consumer in the system (i.e. max amperage out of at least 4 amps)? Or is it somehow determined by some other formula ?


texts: Correct calculation for voltage drop of transistor

texts:
I'm new in electrical stuff, but I know that a transistor has a voltage drop of around 0.7 V. So I have the following circuit:

(Hope it's correct): I want to trigger the transistor if the base get's flow from 3.3 V.
My question: How do i calculate the voltage drop?

$$\frac{5~V - 0.7~V}{50~\Omega} = 0.086~A$$
$$\frac{3.3~V - 0.7~V}{500~\Omega} = 0.0052~A$$

So total at the ermitter:

$$0.086~A + 0.0052~A = 0.0912~A = 91.2~mA$$

Is this correct? Or it is only

$$\frac{5~V - 0.7~V}{50~\Omega} = 0.086~A$$
$$\frac{3.3~V}{500~\Omega} = 0.0066~A$$

or

$$\frac{5~V}{50~\Omega} = 0.1~A$$
$$\frac{3.3~V - 0.7~V}{500~\Omega} = 0.0052~A$$

I don't know where exactly the voltage drop should be in my calculation.


texts: Problems reading a signal with a MCU (TM4C123GXL) input pin

texts:
I'm tring to read a signal generated by an op. amp. with a microcontroller through an input digital pin. All signals I'm working with are DC.

The op. amp. is connected to a light sensor so that it outputs 0V when the sensor is shaded and between 4.8 and 5.2 volts (fluctuates all the time) when the sensor is detecting light. I have measured this signal with a multimeter.

The microcontroller's pin is configured as a digital input with a pull-down resistor. The voltage levels for the pin are a logical 1 if the input voltage is 3.3V < voltage < 5V and a logical 0 if voltage < 3.3.

The problem I have is that when I connect the op. amp.'s output to the input digital pin, and the sensor is enabled, the voltage drops to something between 0.8V and 1.5V, and it doesn't reach a steady level (always fluctuates, wider range than before).

The microcontroller is supposed to change the color of an LED depending on the digital input state. What happens is that the LED blinks all the time. In addition, However, I have connected a steady 3.3V signal coming out of another microcontroller's pin (output) and everything works as expected. In addition, I have measured the voltage at the output pin and it doesn't drop as it happens with the op. amp.

I'm not sure I can connect the op. amp. output directly to a digital input pin. My questions are:

Is the op. amp. output signal considered analog?

If so, if an analog signal has two known 'steady' states, can it be considered a digital signal?

Can I connect that signal directly to the input pin, given that it is still DC? Do I need to connect it to an ADC?

Note: The microcontroller is a TM4C123GXL. I'm configuring the pin PB4 as a digital input and PB6 as a digital output (3.3V). When connection PB6 to PB4, everything works as expected.

EDIT

The schematics is here:

Notice that R3 is a photocell. The op. amp. is a OPA2344

Currently my MCU is powered over USB, from my laptop. Notice that I'm connecting the op. amp. output directly to the digital input pin. Not sure if this can be done.

As you can see I'm using a voltage divider. This is because, if I power the op. amp. with the 3.3V coming out of the regulator, its output is always below 3.3V, so the MCU will never interpret it as a logic 1.

I would like to do this without the help of a transistor.

EDIT 2

I have tried it again powering the op. amp. with the steady 3.3V coming out of the regulator. The output of the op. amp. is steady at 3.3V when the photocell is not shaded, as soon as I connect it to the MCU digital input it drops to 3.29V, so the MCU doesn't detect it as a logic 1.

I have observerd one listake I was doing: I was connecting the MCU GND pin to the common ground. That makes everything 'go mental', I think that is what caused the voltage drop at the op. amp.'s output I saw before. I deduce that it's wrong to connect the MCU GND to the common ground, why?


texts: "Ideal" way of using 3-conductor cable for unbalanced audio

texts:
I am intending to make some short (<30cm) unbalanced audio cables to interconnect devices on a musical instrument pedal board.

As a matter of convenience, I was thinking of using some Belden 9451 three-conductor cable for this because I have a lot of it. It has an insulated twisted pair (red & black) inside a shield wrap. (I wouldn't call it a braid)

Probably overthinking this, but I'm curious if there is a "best practice" for using three-conductor cable for an unbalanced audio signal - some immediate options being;

1 -  twist both inner conductors together for signal, use shield for ground

2 - use one inner (red) for signal, twist black and shield together for ground

3 - use inner twisted pair exclusively..red for signal, black for ground...shield unconnected

or is it all the same when it comes to such short cable lengths?


texts: Speeding up turn-on and off with VOM1271 Photovoltaic MOSFET Driver (/optocoupler)

texts:
It's my first post here so please do not hesitate to tell me if I'm not doing it right :-)

A bit of context : we need to switch an array of power resistors (1,3kW, 1ohms) in order to test under load a battery pack (37V nominal) following a certain load profile. All these resistors will be switched by µC outputs (possibly through a multiplexer).
Basically we're building a poor man's DC load using MOSFETs instead of SSPC.

So we're talking about 37A per power resistor, in order to do this, we've made a small prototype using the astounding number of 2 components :

VOM1271 (the MOSFET driver)
IRFB7530PBF (the MOSFET)

The great thing is that the VOM1271 allow us to make do without an isolated DC/DC and have this very simple BoM. The bad thing is that the rise and fall times are out of this world (in the bad way, talking about mS) and thus we cannot do any PWM if we want to do some load profiles... We can of course still follow the profiles but with 1,3kW steps...

So here's my question : is there a way to speed-up these rise and fall times in order to have acceptable switching losses? I'm not very optimistic about the rise since that only depends on the photvoltaic cell current inside the VOM but what about fall time (which is also the worst)?
Vgs vs. t below

And an another one for the road : what could I add to "ruggedize" this circuit? The 2-components circuit was just to validate the basic principle but I'm guessing there are a couple of basic safety features missing...

Thanks for your help!

Marc

Well it seems that any "integrated power" coupler/gate driver will not give any useable switching speed so we're gonna stick with using it as a solid state relay...

Any input regarding making the circuit bulletproof though?
I was thinking of a 1,7V zener diode in // with the input (the Vf of the input diode is 1,7V). Would that be good practice?

Thanks,

Marc


texts: What does a ADC chip with "2, 4" inputs mean?

texts:
I'm searching through digikey right now and see many ADCs with the input counts listed as "1, 2" or "2, 4". What does this number convention mean?

For example, this Microchip ADC has its input count listed as "2, 4". Looking through the data sheet, I see that it has 4 inputs. What does the 2 in "2, 4" mean?


texts:
I was messing around with a USB camera. I wanted to change the cable because is trimmed but as I was cutting it I saw a small thing (image below). As I was trying to cut the casing and see what it has inside I saw a spark. I tried to connect it with another cable but I don't know if I'm gonna damage the camera or the USB port.

What is it and can I connect the camera without it?


texts: Surface Mount vs Through Hole Aluminium Electrolytic Capacitors?

texts: What are the differences between SMD and TH Aluminium Electrolytic Capacitors? Why are TH variants available with such greater lifetimes? (For example, Digi-key has SMD aluminium caps up to 10k hours, but TH up to 37k hours.) It would appear that the differences extend beyond the way they mount and look.


texts: How to create custom through hole pad shapes in Altium Designer?

texts:
I'm trying to create a footprint for the ACS770 current sensor in Altium Designer (17.1), which has a quitte irregular shaped pad: ('round' pad shape with slot hole, and then a small cutoff in the middle). Does anyone know how to generate such a pad shape?

This is what it should become: (Datasheet)

This is how far I get in Altium:

The via's are no problem, but I don't know how to create the 1mm 'cut-off-space' between the two pads.

Everything I can find on custom pad shapes for altium is with SMD pads, in which case you can just draw a small pad, then extend the surfaces using regions or other primitives, but no results for through hole / multilayer pads...


texts: How to Use SFH235 IR Photodiode Correctly?

texts:
I have an SFH235 ir photo-diode (which datasheet can be found here) and only basic knowledge of electronics.

I want to connect the photodiode to an Arduino (the grand-plan is to add an ir diode and build a distance sensor).

I understand that photodiode produce current, and it produces more current the more intensive the light that falls on it.

I have seen schematics that connect photodiodes the same way that photoresistors are being connected. Others connect it to an "opamp"(why?) And that are also those articles that say I need to amplify the current. I have also seen capacitors added into the circuit.

Which is the correct way for my application? How can I connect the photodiode to the analogue input of Arduino (which measures voltage)?


texts: Which characteristic of a BJT determines the timing in the following given application?

texts:
I currently face a question about the BJT circuit given here:

We see a 2N3904 transistor with constant base current of 2 mA. A switch seperates a 15 V/20 ohm source from the collector of said transistor. Before 1 µs the switch is open. After 1 µs it closes.

What I get from an LTSpice simulation and also see in real measurements is this (Y-Axis is \$I_{ce}\$: collector-emitter current through Q1):

The steady state current of 350 mA is determined by the current gain of the transistor. Base current is about 2 mA in the given circuit.

The peak current of 730 mA is given by (V2-Vce)/R1.

But which characteristic of the transistor determines how long the peak current (730 mA) sustains before the current falls down to steady state current (350 mA?) In this example the time is ~300 ns.

I already thought of the storage time, but it does not really fit, especially if I try different transistors in the simulation and compare the outcome with the corresponding storage time of the transitor in the datasheet. (i.e. 2N2222 has near to 0 time before the peak current decays to the steady state current.)

edit: Added needed information.
edit2: Added simulation result for a 2SD2656 Transistor with rated maximum current of 1000 mA:


texts: How to up-convert PWM frequency without using a microcontroller?

texts:
I am trying to drive a motor H-bridge, but my control system can only support a 400 Hz PWM signal (black box, can't change it) which gives the motor an extremely loud 400 Hz whine as you would expect.

Is there any way to take the 400 Hz PWM signal and convert it directly to a 25 kHz PWM without passing it through a microcontroller (they are verboten for this project)? I can't put the input PWM into an RC filter because I need to preserve the system's time response.

Any ideas? I did a search on Digi-Key for any IC's that could do this, but came up empty.


texts: Finding Absolute Value In Verilog Data Designated by System C/Xilinx X

texts:
I have been trying to find the Absolute value of an integer which is designated to Verilog core using Xilinx C running on Microblaze, what i have seen is that Verilog treats the negative number as a positive number.

I have tried all data types : signed int, int, Xuint32.

My c code is:

signed int data,value;
data=-20;value=0;
putfsl(data,0);
getfsl(value,0);
signed int data1,value1;
data=20;value=0;
putfsl(data1,0);
getfsl(value1,0);

After getting the values of variables I printed them on Hyperterminal.

On my Verilog side the code was:

out <=(in<0)?-in:in;

I also tried this code but results were similar

if(in<0)
   out=-in;
else
   out=in;

Kindly help me out!

I have also tried other data types and changed parameters but results have not worked out to be I always get the same number I input i.e

in<0

statement is not being true, I also tried in<=0.


texts: stepper motor digital frequency and speed?

texts:
In what way the frequency of digital pulse affect the stepper motor funtion.
I want know this because i can send digital pulse through my data acquisition card at rate of 100Hz. I want to run bipolar stepper motor..


texts: Triac gate burns after getting current on it

texts:
I have a T1635H-T triac, that i would like to control with MOC3041. I use typical circuit from the optocoupler datasheet:

The only difference is that i'm using 330Ohm resistor instead of 360Ohm. As a test load i use 40W incandescent bulb.

For some reason, when i enable the optocoupler by closing led-side circuit, triac burns almost immediately with clearly visible clearly visible traces of damage on the gate pin.

What i'm doing wrong?


texts:
I am trying to do a 12 point calibration of a 4 wire 1/10 DIN PT100 using a Fluke dry well and controller. [Accuracy of the Fluke measurement is +/-5mK]

I put a 100.000 Ohm calibration resistor on one of the channels (configured as 4 wire) and see a measured resistance of 100.001 Ohms. So far, so good.

I then take a previously calibrated PT100 (calibrated at Imperial College on a $100k machine). The calibration report shows R0 = 100.006 Ohms for the Callendar Van Dusen equation.

I then put this on the Fluke and the measured resistance at 0degC is 100.306 Ohms - why?


texts: Using a wifi dry contact module (Sonoff) to increase/decrease temperature in a gas water heater touchpad

texts:
I'm a total newbie in electronics, and just started venturing in home automation.
In Brazil there are many different types of tankless water heaters, especially for bathroom faucets and shower. Mine is a somewhat newer model with an LCD display and four buttons: SET, UP, DOWN and POWER.
My goal is to hardwire the UP and DOWN buttons to a dry contact (a SONOFF 4CH Pro) so I can remotely increase and decrease the temperature, much like what you'd want to achieve with an air conditioner. My wife (as most women) loves boiling hot showers, I don't.
I've roughly grasped the concept of NO and NC, and that I would need to wire the two cables coming from the terminals from those two buttons to the NO + COM of two channels in my SONOFF.
The problem is that by looking at the backside of the board, I can't see that second terminal.
Here is a large image of the front of the LCD display, and here's the backside.
The buttons are touch sensitive, and I can see the springs connected to single terminals (R5 103, R6 103, R7 103 and R8 103) as I look at the backside of the board (left side of the image), but I can't seem to figure out that second terminal.
I'm hoping that someone can enlighten me on this one. Cheers!
Edit: I opened up the panel just now and tested by touching both "R5 103" and "C1 223" with either points, one at a time. Every time I did, it would case the sensor to be activated. Any chance to get the same result from a relay?


texts: SCC for Synchronous Generator Using Matlab

texts:
What should I put in ''Three-Phase
Programmable
Voltage Source'' block ?


texts: Flywheel/Dynamo behavior under variable load

texts:
I have a special effects project in mind where I simulate a bellows and coal fire without, you know, actual fire.
My vision thusfar involves rigging a flywheel to a short-stroke lever (the upper arm of a modified bellows), and a bicycle dynamo (or low power alternator, if I can find one for free).  This question is how the generator will act on the rotor connecting it to the flywheel?
Obviously a spinning flywheel without any power being put into it will suffer from two sources of friction loss, the axle's losses to the bearing, and the drag from the surface of the flywheel interacting with the air around it.
My expectation is that whatever load the generator is experiencing is also being felt to the rotor as a sort of drag.
I see three possible interactions here, but don't know which one I'm likely to end up with (or if it's another I haven't even thought of yet):

Any power in the flywheel is being fully tapped by the dynamo,
meaning that regardless of load or rpm the flywheel is being
'rapidly' decelerated by the dynamo; as a consequence, someone going
ham on the lever means you've got a metric shit-ton of excess
power you need to sink somewhere or you're gonna get a real fire
anyway.

The dynamo only takes power off the flywheel to match the load
it's under, meaning that the flywheel will only lose power to
friction otherwise, and you can control the deceleration of the
flywheel by adding or removing load.

The dynamo only lets power out to the load its connected to as
needed, but takes power from the flywheel as fast as it can, leading
to some kind of thermal failure in the dynamo itself.

All of these can be designed around, obviously, but I'm not clear on what problem I'm going to need to be confronting.
The load in this case is negligible: an LED array with more strings being switched on as more power is available to run them.
The desired behavior of the LED array is that a brief period of manual input to the flywheel results in a rapid ramp-up of light from the 'coal bed' which then tapers off much more slowly. Too slowly is better than too fast: I can always add drag to the flywheel.
So, to reiterate the question: what is the behavior of a flywheel/dynamo system in relation to the electrical load being served? What force does the rotor experience as a result of the dynamo's presence? Does that change as the load changes?


texts:
I have this smart plug that allows for a separate ON/OF control of the USB ports. The idea is to use this USB switch to switch another device (230 V/ 500 mA).
For a good price I found these relay modules on Amazon that are meant for Arduino.
My problem: the relay module has 5V input, I guess pins GND and VCC but also a Signal pin. What do I connect to the signal pin from my USB plug?
Thank you for your time.


texts: Replace a one shot thermal fuse with a resetting one

texts:
My mother owns a device for drying fruits and stuff.

Now every year or so, the thermal fuse breaks. I'm always checking if the fan is damages or something else, but the device is always fine. It is just the thermal fuse which breaks for no known reason.

So instead of replacing it with the same type of thermal fuse every time. I was wondering if I could use a resetting thermal fuse.

The current thermal fuse is labeled DYE ZRJG DF110S which seems to be a DF type thermal fuse made by Limitor with a function temperature of 110 °C. The tolerance is listed as +0/-5 K and the maximum rated current is 16 A.

The device has a rated power of 600 W, so the fuse needs to handle at least 2.6 A. It is a resistive heater, so that should be about it.

As I'm not really familiar with these temperature cutoff switches (is that the right product name?) is there a reason why I should not replace the fuse with a cutoff switch?

I could imagine, that if there finally is a failure in the device and it gets turned on and off by the thermal switch, it might cause more damage.

What I want to achieve is, that the device will run for more than a year without having to replace the thermal fuse (but it should still be protected, so a wire is not a solution).

Sorry - should have done this the right way the first time:

simulate this circuit – Schematic created using CircuitLab

After the request by @jsotola for better pictures I took the device apart again. I also removed the control unit cover to understand how the temperature control is implemented.

What I found was: a micro switch is turning on and off the whole device. A (probably bimetallic) bending strip is the temperature control, the knob controls how much pressure is on the strip and thus controls the tripping temperature of the strip.

Close to the thermal fuse (on the other side of the picture I took first) there seems to be another thermal switch, which should probably act as a first safety measure.


texts:
I am trying to figure out a way to get GPS data from a remote source to a Raspberry Pi. The remote source would be a helmet mounted GPS receiver so it would need to be small and preferably inexpensive. A $30 USB GPS dongle would be perfect. The question is how to get the data to the Raspberry Pi board. Line of sight will not always be an option so RF would be best I'm thinking.

I just don't know what to look for. Can someone point me in the direction of some kind of small transmitter/receiver I can use to get the data from the GPS device to the Raspberry Pi? Or if there is some GPS module that has a transmitter built in that would be great too. The typical range of transmission will be between 10 and 500 feet so I suspect that Bluetooth will be out though I don't really know much about the max range of Bluetooth. I really just don't know where to start looking so even some keywords or search terms that could point me in the right direction would be helpful.


texts:
I need some help designing a simple ALU that only can add (4-bit) numbers.
For the design I can only use 4-bit full adders and 4-bit edge-triggered flip-flops.

I am stuck as I do not even know where to start.
Thanks for any help.


texts:
I am using a three wire RTD100 as a temperature sensor.

I know the advantage of the 3 wire RTD100 is that it gives accurate temperature output by canceling the lead resistance. First the resistance between line RED (R1) and BLACK (R2) is measured the total resistance is R1 + R2 + RE and then the resistance between line BLACK (R2) and BLACK(R3) is measured. All three wires have the same resistance i.e R1=R2=R3 therefore we will have to subtract (R2+R3) from (R1 + R2 + RE) to get an accurate temperature value.
I researched about the circuits that I can use with 3 wire RTD100. A Wheatstone bridge is used to find the resistance change in the RTD100.
Circuit 1:

In the above circuit, the wire resistance of the RTD100 is labelled as RW1, RW2, RW3. I understand that the change in resistance will unbalance the Wheatstone bridge.  The output nodes of the Wheatstone bridge are given to the difference amplifier where we get the voltage output corresponding to the change in temperature, but I am not understanding how the Wheatstone bridge and the difference amplifier is canceling the lead resistance.


texts:
In some Intel chipsets the CPU is connected to the Platform Controller Hub (PCH) by a link called Direct Media Interface (DMI). Based on what I found when researching about it, It's a link very similar to PCIe but not from a hardware perspective. However, logically it is considered and configured as such.

The thing that I don't understand is why couldn't the link just be a PCIe bus why do we need something different yet working very much the same. How is DMI different from a PCIe link.


texts: Battery ratings; am I reading this correctly?

texts:
I apologise if this insults anyone's intelligence, but I've always believed the only stupid question is the one you don't ask, so here goes...

As a bit of background, I asked previously about powering a 60w heating element (10v 6A to be precise) and was advised the problem would be solved by using a bigger battery and this turned out to be the case. I bought a lithium polymer battery rated at 12v 10000mAh and that worked, and I heartily thank all of you who helped me with this.

My new issue is this - my (admittedly limited) understanding of battery terminology is that the Ah rating of a battery is how many amps the battery will supply for one hour, so for example a 5Ah battery will supply 5 amps for one hour, 2.5A for two hours and so forth.

I believed that, as the heater needed 6A (or 60w) to operate, if I bought a 12v 8000mAh battery, that would power it, but it didn't; the overload protection on the battery kicked in and prevented it from working.

So my question is this: am I right in thinking that the battery rating of 12v 8000mAh means that this battery should technically be able to supply 8A for one hour? If this is the case, I'm going to ask the vendor for a refund as the battery is not supplying the power advertised. If this is not the case, how do I calculate what size battery I need rather than just keep buying more expensive and (more importantly) bigger and heavier 10000mAh batteries?

As an aside, I am planning to test the batteries by hooking them to heating elements that have known power requirements so I can see exactly how much current they will actually provide before they cut out as opposed to what it says on the label.


texts:
So Im trying to make a solenoid a switch, but I have heard two different ways to power it: AC or DC power source. I learned in class that an AC power source would work because a solenoid is basically an inductor with impedance. Since it has impedance, it needs a frequency to work properly, thus the AC power source, but when I tried it, it didn't work.

I was also told that a DC power source will work, and somehow it did, but the solenoid became very heated. Since a DC power source has no frequency, the current through the inductor should spike up to infinity very quickly, but it took about a minute for the solenoid to become heated a little when I left if connected to the  DC power source.

I just want to know why it works for the DC power source, and not the AC.


texts: Schmitt trigger inverter not properly outputting 5V

texts:
In my project I'm working on right now, I'm trying to use a Schmitt trigger inverter to help debounce input signals. Below is my overall circuit I am trying to implement:

The Schmitt trigger inverter I'm using is the following:
https://assets.nexperia.com/documents/data-sheet/74HC_HCT14.pdf
The transistor I'm using is:
https://www.diodes.com/assets/Datasheets/ZXTN25100DG.pdf
By default, 5V is going into the inverter and 0V is coming out which is what I expect. However when I press the button to connect the inverter to ground, I read that 0V is going in, but only about 1.3V is being outputted. Where have I gone wrong with the circuit?


texts: Is there any bidirectional 5v-3.3v level shifter?

texts:
Is there any IC that interfaces any 3.3V Input/Output to 5V Output/Input? I need it primarily for an Arduino Due but if there any bidirectional IC that works like that it would be great.

Some people advised me to use the SN74AHC125 and CD4050 ICs, but I don't understand how they work or how to interface with them.


texts: Can I use any GPIO pins on the Raspberry Pi for the HX711 Amplifier?

texts: We're going to use an HX711 amplifier to read data from a strain gauge - the SparkFun page says you can use any GPIO pins but it one is "clock" and one is "data." What does that mean in this case? Does that mean in needs to be connected to an SCLK pin? Or can I really use any GPIO pin?


texts:
I often see GDTs are used in series with varistors, like this

E100 is a 1500V/10A GDT, and RV100 is a 1.1KV diode varistor.

For this circuit, I have two question

What's the benefit to combine them in series?
What's the purpose of the 0.01uF capacitor?


texts: I know that the RX interrupt is obviously used to save polling, but why the TX one too?


texts:
I`m designing a control cabinet with a 60A output demand for heaters. The on/off switching of the heater will be done through a 24V/80A contactor(relay). The customer wants the main switch on the door. That requires 2x5x10mm2 wires to and from the door switch. Unfortunately, there is no space for the switch on the DIN rail with a long stick to the door.
I offered 2 solutions:
1. Place the main switch on the side, not on the door.
2. The main switch operates only L1 for the control electronics and L2, L3 going strait to the MCB, and then to the contactor(relay), so I do not need to switch the 60A on the door, only the small current for the control electronics. Is this legal to do this way?
My question is, which solution is the right one? Or if none, then how would you do it?
Thanks!


texts: Cannot debug project using "MPLAB X IDE" on "PIC32 Bluetooth Audio Development Kit" with "PICkit 3 In-Circuit Debugger"

texts:
I have "PIC32 Bluetooth Audio Development Kit" (DV320032) board (with on-board PIC32MX470F512L) connected to a PC via "PICkit 3 In-Circuit Debugger" (PG164130).  After some experimentation I found out how to blink 3 out of the 5 user LEDs on the board.  I use MPLAB XC32 C/C++ toolchain i.e. MPLAB X IDE v3.26 with XC32 v1.40.  I created a new C project using the X IDE, did not change any options, only added a little bit of code into the main to blink three LEDs.

I can run project.  Meaning it builds the application, loads it into the target, and executes it.  LEDs blink happily.

However, when I do debug project, after successful build and programming, I first get pop-up saying that the "Watchdog Timer Enable = On".  I accept the options to change the setting.  It then continues and the next message I get is:

  The target device is not ready for debugging. Please check your
  configuration bit settings and program the device before proceeding.
  The most common causes for this failure are oscillator and/or PGC/PGD
  settings.

I searched for help and found some people suggesting to disable debug i.e. DEBUG = OFF (some people say it makes no difference), I checked and this option in already off.

So my question is: "How can I debug the project?"


texts: Please help to identify this component marked JC 5H on a Rockwell Automation power supply

texts: Please identify the component marked JC 5H on a power supply module from Rockwell Automation.


texts: Noise power at receive antenna with finite transmit SNR?

texts:
I have seen a few examples of link budgets, and they all assume that the total noise at the Rx is just going to be -174 dBm + 10 log BW. However, this seems to me to assume that the transmit signal is perfect and the SNR is the transmit power (dB) minus the noise floor (followed by the noise figure of the Rx chain etc).

I'm having a bit of trouble reasoning through what the effect of a finite SNR on the transmit side would do to the receive noise.  Clearly, the signal level is much higher, but if the Tx SNR is relatively bad to begin with (e.g., 10 dB), what is the received SNR going to be?  I assume that the finite Tx SNR should have some effect, right?

To make things a bit more concrete, let's say radiated Tx power is 30 dBm, path loss is 100 dB, and we have a 100 MHz wide signal with no antenna gain (or loss).  The analyses that I've seen would say the SNR coming off the antenna is 30 dBm - 100 dB - (-174 + 10log 100 Mhz) = 24 dB.  But how can I calculate the SNR if we further assume the Tx SNR was only 10 dB (or 20 dB, or 50 dB)?


texts: How can I remove noise in my preamplifier circuit?

texts:
I need a low noise microphone preamplifier for my Arduino. I used a battery and standard wire but I had noise in my circuit. I need gain 20-20kHz.
Can you help me with the schematic?


texts:
I have a center tapped transformer (12-0-12) and a 24V fan, in order to get the required 24 V for the fan and also bypass the fan noise, I'm thinking of a circuit like this:

simulate this circuit – Schematic created using CircuitLab
Is the "Circuit A" immune to the fan noise in above diagram condition?


texts: What is the (typical) value of SPICE parameter ISS for a (vertical) npn transistor?

texts:
SPICE gives a default value for the (collector) substrate leakage saturation current ISS. The default is ISS=0 but I would like to know the real value for an integrated vertical npn transistor. The transistor is an older high-voltage device used in 1970 until today with many analog chips. The 44 Volt npn in the following figure is what I am interested in using. This figure comes from the "Analysis and Design of Analogue Integrated Circuits", 5th edition, by Gray, Hurst, Lewis and Meyer. BTW, if anyone knows additional SPICE parameters for this device, please provide them or references to them. This book seems to be the only place to get this information which seems a bit strange.

ISS is also known as Saturation Current for Injection and can have a default value = IS Amp. Here is where it fits in the Gummel-Poon model for both vertical and lateral devices (i.e, collector or base substrate leakage saturation current respectively).


texts: Do all I2C devices have separate read and write addresses?

texts:
I'm using a particular I2C device, and when it is connected, I need to write data to it by sending data to address 0x30 but then to read from it I need to read from address 0x31 (or by doing 0x30 | 0x01).

Is it normal to have I2C devices with two different addresses like this?


texts:
I need to control 12 small 12V vacuum pumps with 3.3V coming from a STM32 microcontroller. Those vacuum pumps don't draw more than ~1.5A.
My idea is to use MOSFETs but I'm having a hard time choosing. I have very limited space on my PCB.

What is the smallest MOSFET I can get?

I found this one IRLR8726TRPBF and this one IRLML6244TRPbF but I can't figure out if they are going to work.

Thanks for your help


texts:
I have a 90 V, 1/4 HP, 165 RPM Dayton 2h573 dc motor with 125DV-C driver.
I wanted to adjust max voltage on the driver and accidentally shorted the leads while the motor was running (i left multimeter leads in current measurement mode).
Driver burned for sure and I got a new one but motor does not run anymore. Wondering if i damaged it?

I test both leads and getting 3.5 Ohms  (Not sure what it should be for this motor)
I tested each lead to ground and its open (Both wire and motor casing)
New driver without load (motor disconnected) i get about 80 volts
After i connect the motor, voltage drops to 3.5 volts
Potentiometer is ok. I tested resistance and it goes 0-5ohms

Anything else i can do to verify my motor?


texts: AVRDUDE with buring settings of AVR Studio

texts:
I make my own electronic boards often with an Atmel ATmega328P. I used AVR Studio for programming. Now I tried to make the same settings with avrdude and it looks, that they are not really compatibale.

Is there a way to set the programming speed in avrdude? I want to program my fuses with 2.1592kHz and program my firmware with 500kHz. Does anyone know a command?
It seems that AVR Studio decodes the values for the fuses different than avrdude. Especially the efuse is different. I think these two are the same:

AVR Studio: efuse:0xFD, hfuse:0xDA, lfuse:0xFF

avrdude: efuse:w:0x05:m hfuse:w:0xDA:m  lfuse:w:0xFF:m

Thank you for your hints.

Felix


texts: Help about commands of 16x4 LCD - JHD164A

texts: Can anyone please tell me the commands to display on 2nd, 3rd and, 4th lines of a 16x4 lcd module, JHD164A, i.e; the commands to force the cursor in 2nd, 3rd and 4th lines of LCD. Just like we use 0x0c in 16x2LCD JHD162A to force the cursor to 2nd line. I searched it on internet a lot but cant find it. I am using 89c51 controller and programming it on keil software in Assembly language. LCD module is JHD164A.


texts: Determining max clock speed using a logic tutor

texts:
Data sheets have been provided for all 4 logic gates in the image and I will insert them below as I myself am mostly struggling to understand them due to the majority of information on them. I'm not sure if in order to calculate max clock speed I simply add up all the max tpd delay times or if I need to include transition times or rise and fall times along side these.

Any help would be appreciated


texts:
Some processors have a low frequency mode for using in low power mode.

For example MSP430 microcontroller can work in both

Normal clock frequency 16M Hz
Low clock frequency 32 kHz

I am wondering if in general, sleep mode or low power mode for processors is about reducing the frequency to save power or is it a concept beyond that? What happens in low power mode/sleep mode to save power (on processor)?


texts: Unconnected port warning on reset port in asynchronous register in Vivado

texts:
I've been trying to synthesis this register model. Its simulation in ModelSim is correctly fine. However, when synthesis, it always yields warnings:

[synth 8-3331] design register1 has unconnected port rst

[synth 8-3331] design register1 has unconnected port end_data

Here is the code:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity register1 is
    port(
        rst      : in  std_logic;
        end_data : in  std_logic;
        clk      : in  std_logic;
        D        : in  std_logic_vector(7 downto 0);
        Q        : out std_logic_vector(7 downto 0)
    );
end entity register1;

architecture RTL of register1 is
begin
    process(clk)
    begin
        if rising_edge(clk) then
            if rst = '1' or end_data = '1' then
                Q <= "UUUUUUUU";
            else
                Q <= D;
            end if;
        end if;
    end process;

end architecture RTL;

I don't know what wrong. Could it be my coding style?

Hope you guys could help me. It's been very irritating.


texts: Can I use an Arduino as a USB to serial interface?

texts:
I have a BluRay player that can be programmed by accessing to a serial console, as described here.

I have an Arduino (a Seeduino, actually), that has a USB interface. According to Arduino's documentation, pins 0 and 1 are RX and TX. Do these pins bypass from what the computer sends? Can I use the Arduino as a USB to serial interface for what I need?


texts: I'm reading PCIe specification, which mentions that the communication between the root/end points are through switches instead of buses as for PCI, and this structure improves throughput as the traffic doesn't have to share media with others. However, many pictures of th structure of PCIe switches show that the ports (upstream/downstream) are internally connected using buses. So, is this structure still a switch?


texts:
Do MIS Capacitors discharge completely or only partially due to lack of free charges?

Inside the semiconductor there is a depletion region with no mobile charge carriers so they wouldnt move to the lower potential right?


texts:
It's a very small stepper at 18 ohm resistance per coil(2 of them) (4 phase).

I got: stepper in the picture, L9110, LM358, arduino.

I used an L9110 with the arduino. The stepper moved where it was supposed to move but with a lot of noise, vibrations during some frequencies. At higher frequencies it moved very smooth but at lower frequencies it became a clock. "tick", "tock", "tick", "tock".

I want to step with a sine wave signal. I want it to have an amplitude of 3V. How do I make such a circuit?
3 V / 18 ohm = 0.16 A
3 V * 0.16 A = ½ watt

My previous ideas that have failed:

Use two pins (filtered pwm) on the arduino. Fail: they can only give
20 mA safely. (18 ohm * 20 mA * 20 mA = 0.0072 watt). Too weak.
^Use above idea with two LM358 as buffer for the two pins. Fail: LM358 outputs about 1 mA (0V gnd, 5V vcc).
Use a linear analog voltage regulator. Fail: It will be ineffecient and I don't have a linear analog voltage regulator. Though I could buy one.
Use L9110.  Fail: It only has a truth table. There's no analog voltages.

Since it's just a very small stepper that won't use more than ½ Watt I should be able to get away with a few components.

When it comes to software and digital things I'm a king. When it comes to analog circuits I'm a peasant. Please help this peasant you analog kings and queens.


texts: Trying to build a circuit to boost 5 V DC to 250 V DC with fairly low current output

texts:
I am fairly inexperienced with electronics, but I am trying to build a 250 V DC supply from a 5V source. From research, I have run across charge pumps and boost converters. I tried using charge pumps, and the voltage output wasn't efficient. I ended up using a lot of capacitors and when I put my load on,it significantly dropped the output voltage.

I am now looking into IC boost converters. I ran into some, most notably TPS40210. The data sheet says it can output 260V, but there are no such example circuits. I am wondering if there's a way that is typically preferred to achieve such boost. I am hoping to get a relatively small footprint if that's possible.


texts: Buck/Boost Power Supply: What happens if we use much bigger Bulk Capacitance (i.e. 10x)?

texts:
If we take a buck/boost converter that is known to function correctly, but increase the bulk capacitance by 10x, what can we expect to happen electrically?

Background:
I took the design below off TI's WEBENCH tool. Input: 10-14 V, output 12 V @ 8 A. The total input capacitance is 68 uF (CBulk, aluminum) + 3*15 uF (Cin, ceramic) = 113 uF.

After building it out on a board, I realized there were some serious instabilities occasionally; especially at higher loads, or if the load current suddenly changed. After a lot of debugging I finally realized a larger bulk capacitor (1000uF = 1 mF) upstream was causing it. After removing it, the PSU functioned as intended. In reality, my input stage was:

simulate this circuit – Schematic created using CircuitLab

Now everything is working, but I'd like to understand better before proceeding:

Why did the large bulk capacitor cause the instability in the output?
How can we calculate the bulk capacitor size limit?
Is the bulk capacitor size limit a function of the output capacitors?


texts: Latching circuit for ESP8266 with coin cell and Reed Switch

texts:
I am trying to make a circuit referencing to a YouTube video to make my circuit last long on a battery cell (CR2032). I don't know where is the problem but here is the schematic diagram I created

https://easyeda.com/nehul.splendit/ESP-door-sen-mo

With this circuit the problem is. Its not turning ON the ESP-01s at all.

I am not sure where I am wrong. As per my understanding I am making same as per the reference video https://www.youtube.com/watch?v=n_A_8Y4xNx8

Any suggestions where is the problem in my circuit?

Here is how i have my code sketch:

int count = 0;
void setup() {
  pinMode(0, HIGH);
  digitalWrite(0, HIGH);
  pinMode(2, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {

  digitalWrite(2, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(2, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
  count++;
  if(count == 5){
    delay(5000);
    digitalWrite(0, LOW);
    ESP.deepSleep(0);
  }
}

Thank you!


texts:
Greetings all,
             Just to be clear, I am not asking anyone to do my homework. I am simply asking for guidance and or to clarify any conceptual errors I am making. For the following question, I can get the length of the impedance of the factory load by Vrms/Irms. And I can write that as \$ 7.36864\cos\theta + j7.3684\sin{\theta} \$. I also know that the total impedance the source sees has a length of 7.3684 because of Ohms law. So I had an equation where I had the real parts and imaginary parts, square them and it must equal 7.3684. and I know have the angle of the impedance for the factory load, so I know have the imaginary and real part of the load. But I am uncertain where to go from here. Work is attached below.


texts:
Can anyone suggest an active pullup circuit to replace a typical pullup resistor for an arduino one wire network of ds18b20s? I have 80+ meters of network in a daisy layout of 12 sensors. I've reduced the pullup to 1k, but still having issues with too large a rise time due to capacitance of wire. Read elsewhere that an active pullup could do the job, but no details of a device/circuit.
Thanks


texts: Am I correct in assuming voltage is used to describe two different concepts?

texts:
I am hobbyist trying to gain a strong understanding of the basics of electronics.
So far I have been confused in trying to understand voltage and its relationship with current by its use to describe what seems to me to be two different concepts.
One concept is the force a voltage source applies to a conductor to get current flowing.  The other concept is the amount of energy required to get a charge from one point to another.
For example, the energy required to move an electron through a resistor. Is my understanding here correct?


texts:
I have a PIR sensor module based on BIS00001 IC. I am using the 3.3 VDC output signal of the sensor module to trigger an LED matrix using a low side NPN transistor and a current limiting resistor.

simulate this circuit – Schematic created using CircuitLab

However, the problem is that after the preset time of the sensor, the LED resets, turning off, instead of continuing to remain ON if the human is present in a steady position. It remains ON if the human is in constant motion.

I have come across an article with some details on the PIR light controller which uses 555 timer as a missing pulse detector. However, I am unable to comprehend if it can keep the light source ON even when the IR source is not in motion.

http://electronicdesign.com/analog/pir-light-controller-relies-missing-pulse-detector

Is there a way keep the LED ON, even when the human is in steady position and not in motion?


texts: What is the resulting Voltage Transfer characteristics of the modified CMOS-inverter circuit if NMOS and PMOS are interchanged?

texts: What is the resulting Voltage Transfer characteristics of the modified CMOS-inverter circuit, if the positions of \$NMOS\$ and \$PMOS\$ are interchanged?


texts: Role of Capacitors with additional power regulator

texts:
I have a a 7805 voltage regulator that has a capacitor on input and output.  The 5v from that regulator is then elsewhere in the circuit stepped down to 3.3v with another regulator.  I am wondering if i then NEED a capacitor on the input of the 3.3v regulator?
Am i misunderstanding the effect and purpose of the capacitors in this situation or do i always need capacitors on the input and output regardless of the situation.

thanks.


texts: Are the emissions to power electric cars really better for the environment than the emissions from petrol cars?

texts: In my country most of the electricity is generated by coal which is then in turn used to power electric cars, which I don’t think is to good for the atmosphere, is there any prof that this is better for the atmosphere than the emissions from a petrol engines in the majority of cars ?


texts: Respecting setup/hold time in RTL design

texts:
This question might sound obvious for some, however, I found that I need to understand some VLSI fundamentals.

In Functional simulation setup and hold time are equal to zero, so we can simulate the design and have a data transition at an exact rising edge. My question is, once we simulate the RTL and validate its functionality, how to be sure that the synthesized design respects the setup time, in the context of FPGA and ASIC? Does the compiler add some delays automatically according to the gates library, so a data transition will happen after a clock edge? Do we need to set setup time with some constraints especially when dealing with ASIC?


texts:
The IR2101 is an high and low driver typically used to drive MOSFET half bridges.

On this blog, it is said (IR2110 is almost the same as IT2101):

  "IR2110 can't be used to drive both high-side and low-side MOSFETs simultaneously"

The only indication about that specific point I can find in the datasheet is the sentence:

  "The output drivers feature a high pulse current buffer stage designed
  for minimum driver cross-conduction"

However the functional block diagram doesn't mention any exclusion of the HIN+LIN case, and they also show examples where HIN and LIN are switching from low to high simultaneously.

So, do you think I can cross-conduct my half-bridge by setting both pins to high with this driver?

Thanks


texts: How to make sense of speed vs Torque curves in speed control mode

texts:
I am operating my motor in closed loop speed control mode using motor controller. Toque vs speed curves gives us a relation between them which is one-one correspondence. But in a closed loop speed control operation by keeping the load constant when one can always vary the set speed. Which means that for a given load(torque) there can be multiple speeds ?

Is torque Vs speed curves apply only in open loop ? Do it make sense to look at them in closed loop control.

Am I missing something in here ?

Thanks


texts: Control 24VAC solenoid with arduino using a octocopuler and a Triac

texts:
Following a previous question I implemented the following schematic on my PCB.

The schematic :

My PCB:

I have been unable to make it work, if I measure the voltage on j13 it's allways 25v, i know the controller is working because D2 Led is on for 5 seconds and then off for 5 seconds.

If I remove R20 J13 is always 0v.
If I remove the MOC3012 j13 is always 25v.
I have replaced U2 and Q1 with brandnew ones just in case they where fried but it makes not difference

I have been scratching my head all day long trying to figure out what's wrong with my implemention but I can't find where is the problem.

My adrduino code :

void selfTest()
{
int counter = 0;

/* Clears the LCD screen */
lcd.clear();
lcd.setCursor(0, 0);
lcd.print(F("Self Test"));

/* This routine never stops */
while (true)
{
    diagnostic.turnOn();
    delay(100);
    diagnostic.turnOff();

    /* Updates the counter test */
    lcd.setCursor(0, 1);
    lcd.print(counter);

    /* Acoustic notification */
    beep();

    /* opens the valve and waits 5 seconds */
    openRelay();
    delay(5000);

    /* closes the valve and waits 5 seconds */
    closeRelay();
    delay(5000);

    /* increment the counter as 1 complete open/close cycle */
    counter++;

    diagnostic.turnOn();
    delay(100);
    diagnostic.turnOff();
}
}

Edit:

Added J12 which is the connection to the 24VAC power supply.


texts: Should I add bypass capacitor for every IC and Microcontroller?

texts:
I am expecting a noise from a Power Source caused by motors.

However my setup already includes a buck-converter, and have the input and output capacitors. Should I add bypass capacitors for the powers on the IC's and Microcontroller like the Particle Photon. What will be its effect since it would add up capacitance values since they are all parallel.


texts: Unexplained voltage drop in input clamping & buffering circuit

texts:
I'm designing a circuit consisting mainly of 74LS series logic. I am clamping and buffering several input signals using a zener diode and a 74HC7014 Schmitt trigger buffer. A relevant excerpt of the schematic is below, for the simplest case of the problem I'm seeing. (The rails on the 74HC7014 and the 4066 are T-GND and T-VCC. T1-7 and B1-7 are connected. The 2N3904 part is just a discrete inverter.)

When I construct precisely this circuit on the breadboard using through-hole components, everything works as expected. When DIVSW is closed, points A, B, and C all measure pretty close to T-VCC.

However, on the PCB I had manufactured with SMT components, when DIVSW is closed, point A measures at T-VCC as expected. However, point B measures approximately 2.8V, and point C measures 0V. I understand neither why the buffer input would be at 2.8V in the first place, nor why the buffer output would be at 0V given that fact (74HC7014 high trigger level is 0.65V). Edit: that should read 0.65 x VCC, which does make sense.

I can't see any significant differences between the through-hole components and their SMT counterparts, and all the traces appear to be correctly connected. I am using the same power supply in both cases. I also tested this on two separate SMT PCB prototypes with similar results (one has since been hacked up in an attempt to diagnose).

I am stumped as to what could possibly be going on. Any suggestions on where I might start looking? Happy to provide any additional details needed.


texts: Simplest, cheapest way to detect if a motor is running?

texts:
I'm trying to design a system that automatically logs the run time of several machines. What time they start, what time they finish, how many hours they ran during the day.

All the machines I want to track use motors, so at first glance, it seems like it could work to log the amperage used by the motors.  However, I don't actually need the reading for the number of amps, I just want to know the time the machine turned on and what time it turned off, I don't need to log all the numbers in between.

Does anyone know if an Arduino would be able to help me record the start/stop time only? Or have a better idea of how to track this? Thanks for your thoughts.


texts:
We are using some tantalum capacitors for some products. for two purpose:

Bulk Capacitor
Low ESR for MCU power

Recently, we are suffering to get tantalum capacitors. Our supplier is saying that Chinese electric vehicle companies are using huge amount of these. So it makes the shortage of tantalum capacitors

So we need to replace the tantalum capacitors with another type of capacitors.

I think that the characteristics of the replace capacitors for Bulk is not important. So we have only to meet the its capacity, voltage and dimension.

Which types of capacitors will meet for the replacement of bulk tantalum capacitor?
Which types of capacitors will meet for the replacement of low ESR tantalum capacitors?

FYI, I can't change my PCB so the the 2D dimension should be same. (We are using A type and D type tantalum capacitors)


texts: Stealing energy from radio towers or power lines

texts:
From this answer: How much energy can be harvested from nearby radio towers or power lines?  What circuits would you use?  How much would you have to absorb for it to be noticeable by the producers or by other consumers?

I see a lot of stories, rumors and anecdotes online, but I'd like facts and references better.


texts: Should I be using a Standard Kalman Filter (KF) or an Extended Kalman Filter (EKF)?

texts:
So I am trying to implement a Kalman filter for an Inertial Measurement Unit (IMU) using an Arduino.

I have 4 sensors:

GPS
Accelerometer
Gyroscope
Magnetometer

To measure various vehicle properties such as velocity/acceleration/position/roll/yaw/pitch. I'm struggling to understand if I should be using a standard (KF) or EKF filter.

My guess is standard filter is fine as the sensor values have a linear relation to what I am trying to measure, but i'm not 100% sure on this.

Can anyone provide any insight? Thanks.


texts: Why crystal capacitors have to be close to each other?

texts:
Atmel's AVR186 document shows in page 2 a layout of two capacitors very close to each other and pointing in the same direction, also in page 3 they say: "The load capacitors should be placed close to each other." (despite "Reduce the parasitic capacitance between Xtalin and Xtalout pins by routing them as far
apart as possible." which sounds contradictory).

I wanted to know why to place them like this, so close to each other. My guess is since there is apparently an inversor amplifier inside the MCU, the current in them is always in opposite direction so the induced magnetic fields will cancel with each other and it's inductance will better. But I am not sure this is the reason and if the current is circulating in them in the same direction, this can be twice as worse since the fields will couple adding each other.


texts: Does a BJT optocoupler have an inherently short circuit proof output?

texts:
I want to use an NPN optocoupler (ACPL-214) to drive an offboard relay. I know how to size the input resistor to limit the LED current to 20mA. This will cause the output current to be in a certain range (depending on CTR and other factors.)
Question 1: Is this opto output short circuit proof (since the input LED current is limited?)
Question 2: Does it matter if the opto is used in a high side configuration (collector connected to battery, emitter connected to the relay coil) or low side configuration (collector to relay coil and emitter to GND?)
High Side

Low side

Question 3: Do the answers above apply to normal silicon BJT transistors if the base current is limited?
The question might be trivial but I fear that shorts can cause some kind of current transient that could blow the transistor.


texts: How to determine if given OpAmp model supports single supply (Ex. OPA167x)

texts:
Reading OpAmp datasheets I often struggle with the task of determining whether a given model of OpAmp can be used with single supply or not.

Sometimes, there is a plain statement in the features. But most of the time, it is not explicitly written. For example, in the OPA167x datasheet, the manufacturer only says

  Wide supply range:–  ±2.25V to ±18 V, or 4.5 V to 36 V

I guess thats enough information here, but are there any other cues (or words) that I can look for? Due to english not being my native language I might miss something.


texts:
I was trying to control a stepper motor using ATmega32. i am using AVR studio 4.But, it is not working perfectly at simulation at Proteus. The 4 input signals for motor driver pin IN1, IN2, IN3 and IN4 are blinking without any sequence.  My code is following -

.include "m32def.inc"

.DEF TEMP = R16
.DEF COUNTER = R17
.DEF _STACK = R18

.ORG $0000

LDI TEMP, 0XFF
OUT DDRB, TEMP

LDI _STACK,LOW(RAMEND)   ;SETUP STACK POINTER
OUT SPL, _STACK          ;SO CALLS TO SUBROUTINES
LDI _STACK,HIGH(RAMEND)  ;WORK CORRECTL
OUT SPH,_STACK

LABEL1:
LDI TEMP, 0b00000001
OUT PORTB,TEMP
RCALL PAUSE

LDI TEMP, 0b00000010
OUT PORTB,TEMP
RCALL PAUSE

LDI TEMP, 0b00000100
OUT PORTB,TEMP
RCALL PAUSE

LDI TEMP, 0b00001000
OUT PORTB,TEMP
RCALL PAUSE

RJMP LABEL1

;----------------;
;DELAY ROUTINE   ;
;----------------;
PAUSE:
LDI COUNTER, 2
PLUPE:
NOP
 DEC COUNTER
  BRNE PLUPE
   RET


texts: What kind of cable is used to connect the two parts of headphones

texts:
I am trying to replace a broken cable on my headphones(Sennheiser HD 280 PRO) but I can't figure the type of cable so that I can order it online. I think it is pretty standard as it seems other headphones have similar cables. However searching for headphones cable only helps to find replacing connector cable(i.e. the one connecting the headphones to computer) but not the one connecting the two parts(speakers).

This is a picture of the cable. One part is varnished(maybe not the correct word in English). I don't have a caliper, but I think the tickness of the cable is about 1.5-2mm.
Could someone please tell me what kind of cable is this?
EDIT: adding two more pictures of the end of the cable:

The while bit that can be seems is more like fabric, not wire.


texts: Where are the cathode and anode of this diode?

texts:
I have a 1N4148 diode. I can not find which is the anode and cathode from datasheet.

Does anyone know where is the anode and cathode of this diode are?


texts: VGA Timing - Sync & Porch Positions - FPGA

texts:
I've been programming a VGA Module in verilog, and have spent some time fighting with my monitor to display some test colours. When referencing VGA timing diagrams online, it seems many are similar but the front, back & sync pulse positions are switched around.

I've managed to get it working using either orders below (for both vertical and horizontal)

Sync, Back-Porch, Display, Front-Porch
Front-Porch, Display, Back-Porch, Sync

However I have tested these (and they didn't work):

Display, Front-porch, Sync, Back-Porch
Front-Porch, Sync, Back-Porch, Display

I have confirmed through simulations that all tests were behaving as expected, although the monitor did not accept the second set above.
(I do hope that I didn't somehow manage to stuff up the non-working set above)

This timing diagram worked:

This other diagram on google didn't work:

I do understand the purpose of the porches & sync pulse, but with non-CRT monitors, does the position of these have any importance? Or is my test monitor (an old Acer) somehow not handling it? I haven't yet had a chance to test it on another monitor.

Any Input, or links to material would be appreciated.


texts: `sizeof` Function Is not Working as Expected With AVR Microcontroller

texts:
Observe the following example code (Microcontroller used: ATtiny84A):
void toggle_output(unsigned char *string)
{
    for (unsigned char i = 0; i < sizeof(string) - 3; i++)
    {
        PORTB ^= (1 << PORTB0);
    }
}

toggle_output("test");

I would expect the pin, which is attached to port B0, to toggle 4 times - once for each character in "test"; however, what is happening is that I am ending up with an endless loop. The pin is endlessly toggling when it should only toggle 4 times.
I know that the pin is functioning normally, as I am able to set the output statically high or statically low. And I know that If I give the for loop a fixed number of times to loop, it will do so the expected amount of times. For example:
void toggle_output(unsigned char *string)
{
    for (unsigned char i = 0; i < 5; i++)
    {
        PORTB ^= (1 << PORTB0);
    }
}

toggle_output();

The above code will cause the pin to toggle 5 times as expected. So for some reason the sizeof operator is yielding some enormous number, or the microcontroller is, for some reason, adding to it. What is even stranger, is if I write an equivalent C program on my computer that just prints a number for each character in a string, it does so as expected:
void number_for_character (unsigned char *string)
{
    for (i = 0; i < sizeof(string) - 3; i++)
    {
        printf("1");
    }
}
number_for_character("test");

OUTPUT: 1111

What is going on here? Why isn't the sizeof operator working with the ATtiny84A?


texts: What's the maximum supply voltage for a OPA2134PA?

texts:
I built a MOSFET driver using a TI 741 op-amp, sounds like garbage - because you know... its a 741.

I decided to continue my endeavors and purchase some better preamps and settled on a half-dozen TI Burr-brown OPA2134PA.

I know this is a basic question, but I would really appreciate the assistance:

What is the maximum supply voltage for this IC? I've got a dual DC 16v (36v total) supply. Will that cause issues?

I'm afraid I've fried all of them because they got EXTREMELY hot just by connecting the power pins. I even tried reducing current by connecting a 4.7k resistor between pin-7 and my positive supply - it still got super hot and produced no output! I'm at a loss!

IC in question:
https://www.mouser.com/ProductDetail/Texas-Instruments/OPA2134PA?qs=7nS3%252bbEUL6uyT34OzaiM4g%3D%3D


texts: Inductors short at DC or does it have a voltage drop?

texts:
In previous courses, I remember we were told that capacitors act as an open circuit at DC and inductors act as a short circuit.

I came across this video:
https://www.youtube.com/watch?v=WR6qVvnDnI4
and in this, it has a DC source.

Now with my previous understanding, does this mean that all the voltage is actually dropped by the non-ideal series resistance of the inductor?

I'm just trying to make connections between different courses I took/am taking.


texts: frequency divider by 42 with 50% duty cycle

texts: I want to design a clock divider by 42 from flip flops. Is there a way to do that while still gets 50% duty cycle?


texts: What is the name of this DC-DC converter topology?

texts:
I spotted a circuit in the wild that generates symmetric (e.g. ±8 V) analog power rails from a single +5 V supply using a single boost converter and a single 10 μH inductor. This is a very common use case so I spent some time to reverse engineer it. The following is a schematics/simulation I made:

U1 and V2 are my make-shift PWM power switch for simulation --- in the actual circuit the net is tied to the SW pin. Of course the positive output is regulated through feedback, but the negative output is not directly tied anywhere.

I found a post by Linear Technology that briefly mentions the negative branch of this circuit as a "inverting charge pump" (Fig. 4), but I cannot find other sources on this topology. The positive branch seems to be just flipping the direction of the two diodes, making it slightly different from the original boost topology...

So what is this really? And what are some advantages/disadvantages of this design compared to e.g.:

Separate boost and inverting converters (e.g. TPS65131 which integrates both), which requires 2 inductors
Boost converter followed by a fly-back-capacitor-type inverting charge pump

2017-03-19 EDIT:

After some digging I found this these links:

Simplest possible 5V to +/- 10-15V converter (for op-amps)
Inverting charge pump with boost converter loading characteristics
http://www.ti.com/lit/an/slua288/slua288.pdf
https://obsoletetechnology.wordpress.com/projects/studio-electronics/dc-dc-bipolar-power-supply-for-effect-pedals/

As I expected this is a very common use case. I think at this point I just need a textbook or equally authoritative source that documents the fundamentals of this topology. Any suggestions?


texts:
I'm working in a buck converter to step down 127VDC to 5VDC/1A. I know that boost converters have limitations, thus it's not recommended to step up 5VDC to 127VDC. But I couldn't find anything about buck converter limitations. After Reading this document from TI I figured out some values for inductors, capacitors and so on. But my doubts still remain: Is it okay to step down that amount of volts? Will I find any trouble with my common buck converter circuit?

Obs.: The load will be constant and it is not sensitive to voltage oscillation around the 5V tension.

simulate this circuit – Schematic created using CircuitLab


texts: Can I measure analog voltages for a circuit with multiple power supplies?

texts:
I have two components in a circuit: An Arduino Uno R3 and a Wind Sensor Rev. P. See diagram below. The wind sensor requires 12V to operate, so I powered it with an external power supply (provides 12V DC at 1A). The wind sensor outputs an analog signal up to 5V with the sensor reading.
I would like to use my arduino's analog-to-digital converter to read the sensor value. But can I do this if the arduino is powered with a different power supply? I have it connected to my laptop with a 5V USB cable.
I tried reading the value but I get fluctuating readings. To debug, I made a few more connections from the analog-in pins. As seen in the diagram, I can read voltages correctly if they are from the arduino. But if I try to read any voltage from the external power supply, the value is random.
I used a multimeter to check the voltages in the external power supply are 11.20V (close enough to 12V) and the voltage from the sensor OUT pin is 1.40V (within the 0V - 5V range I expected).
So why can my arduino not measure these voltages? I assume it's because the two different power supplies are changing the frame of reference for the ADC pin. But it's not clear to me, so I would appreciate a conceptual explanation.
My intuition tells me that both power supplies should share the same GND pin. But I didn't want to connect the GND between the two power supplies together, given they operate at different voltages and currents. Is this safe to do? Or should I just get a power supply module that will allow a single power supply to output both 12V and 5V?


texts: I'm hooking up some 3 phase transformers that have multiple taps and I need to know the exact service voltage. Phase to ground averages 290 volts. 1 -2 = 498 volts, 1 - 3 = 501 volts and 2 - 3 = 506 volts.


texts: Input impedance from RC filter to inverting and non inverting op amp

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I am building a preamp for a sinusoidal current source. I have a two stage amplification process, with a bandpass RC filter in the middle. The second stage amplification is has two outputs from an inverting, and a non inverting OP-AMP. I want the output from both inverting and non-inverting amps to be as close as possible, but inverted. I also require V_out/V_in for the second amplifiers to be about 20 and -20 for the inverting and non-inverting respectively. This would normally mean $$-R7/R6 = -20$$, and $$1+ R4/R5 = 21$$

I have two questions.

Firstly, for the inverting amp, does the resistor in the bandpass RC filter (R2) affect the amplification of the inverting OP-AMP? Making the gain $$-20 = -R7/(R2+R6)$$ Would R3 have any effect too?

Secondly, for the Non inverting OP-AMP, as the input inpedance is infinite on the +ve input anyway, does R2 make any difference?


texts: Current limiting on a stepper controlled by L293D on an arduino board

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I currently have a bipolar stepper motor connected to a l298n, with one resistor to each coil.

The problem is it draws a lot of power when there is no need to, and limits the maximal power of the stepper.

The l298n is connected to an arduino. Can i use the arduino pwm to limit the current?

I already tried with the Enable pin on the l298n board, but the motor did not work correctly.

This thread is similar to my question, but it doesn't clearly answer the question Is it possible to run a stepper motor only with a L293D at reduced current?

EDIT1:

I have 2 bipolar stepper motors(phase current 1.6A), and 2 l298n controller boards.


texts: Which voltage regulator should I choose to power STM32 + 4G module + GPS with low consumption when they're in stand by?

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I'm trying to design a 4G tracker that uses a 4G module and a GPS receiver. The 4G module, as the datasheet says, uses a maximum of 600mA when connected through 4G + audio working, so this is the theoretical maximum consumption the 4G module will have. The GPS I didn't choose yet but I guess it'd consume less then 200mAh.
I'm planning to communicate (through UART) with the 2 modules though an STM32L011F3UX which is ultra low power, so it'll consume very low current.
That's why I've chosen the AMS1117 with a 3.3v output, it has 1A of maximum output which I think will be enough for all the things. I didn't add the decoupling capacitors for the GPS and 4G modules yet, I'm gonna research on how I should do it.
The circuit for the AMS1117 is intended to power the STM32, 4G and GPS modules, but the decoupling capacitors on the right are for the STM32 only.
I'm mainly concerned if this power circuit is ok for these demands.
Also, the idea is to keep the 2 modules idle/in stand by for the majority of the time, like 95%! So the idea is to not waste energy. Can I trust that the AMS1117 circuit will only consume power when needed? If I need to update the location every 20 minutes, then I might need less than 150mA for the entire circuit in stand by mode for these 20 minutes, and only high consumption (possibly 800mA, let's say) for some seconds, maybe 5 seconds.
I'm grateful for any help, and I'm gonna make all these circuits and code open source.
The 4G module is a Toby-L210 https://www.u-blox.com/en/product/toby-l2-series


texts:
I'm planning to make a drum controller (something like arduino) for pc using a piezo transducer as sensor, some electronic circuit, keyboard PCB connected to usb and sampler for drums in pc. I found out that some people have similar plan, but they didn't finish it.
So my plan may look like: I hit the piezo, signal will be amplified with OP amp, then I need something what basically connect two contact in keyboard (e.g. for letter "A") or just lower resistance between them under 40k with with the piezo signal. I used transistor as switch. Hope that you understand it. I designed scheme below, but it doesn´t working. Please help.

Keyboard PCB


texts: evaporator circuit problem with BU407 overheating

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Using the standard circuit from YouTube but the mist is not at all efficient and I’m burning out transistors on overheating. Where am I going wrong, please?
I purchased the components locally from a specialty shop.
Kindly see attached circuits tried. Both give a very high heating of the BU407 (to destruction).
Below are the images of the various circuits tried:
1st Image (Imagination)
https://youtu.be/HGfFsQ3viwk

The second comes from https://youtu.be/7XEkeVaJEFQ
where I tried this one with 4.1K and 120 Ohms and replaced the 4.1 with 3.3K and the 120 Ohm with 100 Ohm, both did not give efficiency, but noted that the current requirement dropped slightly when the 4.1K resistance used.

I also tried various inductance values ranging from 18 to 60 micro Henry still with no luck...
The real issue here is two fold:

a) the BU 407 very much overheating despite the sink size (the same goes for BU406 and TIP 41CV transistors.
b) the efficiency of the vapor is very much missing.... I'm using a 25mm ceramic disk marked BT86.

I'm a mechanical engineer as well as a petroleum engineer, hence my experiance with electronics is slim, particularly as I graduated in 1980 where they were hardly any real electronics around.
I would appreciate if someone could suggest what I should be changing in any of the circuits presented, else If anyone can suggest a different simple similar circuit that I can try.
I have added two pictures for my circuit used (front and back)