texts:
I'm trying to implement a "button pusher" with some transistors controlled by an ESP-01 module, to push buttons on a remote control. I'm having an issue where if when the GPIOs (I'm using 0, 2, and 3) are connected to the base of the transistor (via a 1k resistor) when I apply power, the ESP will not start and the transistors (2n2222) are in the on state. The red light comes on, the blue light flashes very briefly, but the LEDs I'm testing the transistors with are on, and ESP never starts broadcasting its network. If I disconnect the GPIO 0, 2, and 3 pins, power the ESP, then reconnect them then everything works fine until reboot. Here is a portion of the circuit, the real one has 3 transistors, but they're all set up the same.

simulate this circuit – Schematic created using CircuitLab

And here's my code:

#include <ESP8266WiFi.h>
#include <DNSServer.h>
#include <ESP8266WebServer.h>

const char *ssid = "RemoteControl";
const char *password = "********";
const int button1 = 0;
const int button2 = 2;
const int button3 = 3;

const byte DNS_PORT = 53;
IPAddress apIP(192, 168, 1, 1);
DNSServer dnsServer;
ESP8266WebServer webServer(80);

String webpage = "<!DOCTYPE html><title>Remote Control</title><meta name='mobile-web-app-capable' content='yes' /><meta name='viewport' content='width=device-width' /><button onclick='handleEvent(1)' style='width:100%;'>
1
</button>

<button onclick='handleEvent(2)' style='width:100%;'>
2
</button>

<button onclick='handleEvent(3)' style='width:100%;'>
3
</button>";

void handleRoot() {
  String button = webServer.arg(0);

  switch(button.toInt()) {
    case 0:
      // initialize webpage
      digitalWrite(button1, LOW);
      digitalWrite(button2, LOW);
      digitalWrite(button3, LOW);
      break;
    case 1:
      digitalWrite(button1, HIGH);
      delay(250);
      digitalWrite(button1, LOW);
      break;
    case 2:
      digitalWrite(button2, HIGH);
      delay(250);
      digitalWrite(button2, LOW);
      break;
    case 3:
      digitalWrite(button3, HIGH);
      delay(250);
      digitalWrite(button3, LOW);
      break;
  }

  webServer.send(200, "text/html", webpage);
}

void setup() {
  pinMode(button1, OUTPUT);
  pinMode(button2, OUTPUT);
  pinMode(button3, OUTPUT);

  digitalWrite(button1, LOW);
  digitalWrite(button2, LOW);
  digitalWrite(button3, LOW);

  delay(1000);

  WiFi.mode(WIFI_AP);
  WiFi.softAPConfig(apIP, apIP, IPAddress(255, 255, 255, 0));
  WiFi.softAP(ssid, password);

  dnsServer.start(DNS_PORT, "remote", apIP);

  webServer.on("/", handleRoot);

  webServer.begin();
}

void loop() {
  dnsServer.processNextRequest();
  webServer.handleClient();
}

Is there something I'm doing wrong, or is this something unavoidable with the ESP itself?


texts: create truth table of subfunctions based on main function truth table

texts:
I have a question about the below truth table and logic functions.

I need to create the truth tables of the subfunctions based on the information given. There is no information on which gates are being used so i am not sure how to construct the truth tables.

$$\begin{array}{|cccc|c|cccc|c|}
a & b & c & d & H & a & b & c & d & H\\ \hline
0 & 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 1 & 0 & 1 & 0 & 0 & 1 & 1\\
0 & 0 & 1 & 0 & 0 & 1 & 0 & 1 & 0 & 1\\
0 & 0 & 1 & 1 & 1 & 1 & 0 & 1 & 1 & 1\\
0 & 1 & 0 & 0 & 0 & 1 & 1 & 0 & 0 & 0\\
0 & 1 & 0 & 1 & 0 & 1 & 1 & 0 & 1 & 0\\
0 & 1 & 1 & 0 & 1 & 1 & 1 & 1 & 0 & 1\\
0 & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1 & 1\\
\end{array}$$


texts: I am trying to build a voltmeter, but the voltmeter is powered by a 12V dc adapter.  My concern is if the ground potentials between the analog input source and the voltmeter are different (e.g. due to different power outlets), ground current will start to flow, corrupting the voltage reading.  Is this concern real?  If so, how should I fix this at circuit level?  I am thinking of isolated buck with isolated ADC.  Thanks.


texts: Determine voltage with which to run COB LEDs

texts:
I have a few COB LEDs laying around, but unfortunately I don't know the exact model anymore.
Hence I can't read their data-sheet.
However, I would still like to use them. I own a good multimeter, and figured it might be possible to use it to determine some characteristics of the LEDs, so that I can figure out what driver to power them with.
Can you recommend to me a certain procedure to do this, that would allow me to find some "optimum point", where the risk of damaging the LEDs is relatively low, but where I don't have them running way under their potential?
When I talk about "risk of damaging", I refer to the risk of damaging them during operation - if I happen to destroy one or two during the initial measurements, that would still be worth it.
I found this thread that treats a related question, but there the topic is LED-panels, and I have COB-LEDs, so maybe there are some differences..
I also know the driver which I used to power multiple of them in series - it was the HLG-185H-C700A - but I don't know the exact number of LEDs I used to power with that driver (might have been btw. 6 and 8 I think).
However, what we can conclude is that the operating current of the LEDs is 0.7A.
The reason I won't use that same driver again is that I don't want to run as many LEDs as I used to.


texts: How do I create circular polygon pour cutout in Cadsoft EAGLE?

texts: I would like to have a cutout without copper within a polygon pour.  I tried to draw  a circle on the top layer but to no avail.


texts: Op-amp - Slew-Rate vs Exponential Output

texts:
I'm having some difficulty understanding why an op-amp has an exponential response even if its slew-rate is infinite?
Isn't the exponential response of the op-amp output caused by the parasitic capacitances of the internal op-amp structure (CGS, CGD, etc.). And the slew-rate is caused by output capacitance?
I'm having some trouble distinguishing the two. I always thought that the exponential response of an op-amp to a step input was due to capacitances.


texts:
In rf electronics, we often characterize a component or antenna by its standing wave ratio (SWR). What is the definition of this parameter and how does it affect a circuit?

The motivation for this question is that while answering another question, it would have been useful to be able to refer to a definition of SWR within the site in order to explain how the SWR is measured.


texts: How does one calculate the input impedance of a tube based preamp?

texts:
I'm finding tons of information and equations on calculating this for solid state devices, but nothing for good old fashion particle accelerator based amplifiers :P

Currently I'm revamping the K270 guitar preamp to use components that are readily available. See the original design here: http://s13.postimg.org/patw5krxj/k270.png

This is my current progress: https://123d.circuits.io/circuits/852190-jan-6418-vaccum-tube-valve-preamp

Here is a snapshot at the time of writing this:

The problem I think I might run into is that my guitar's pizeo pickup requires a ridiculously high input impedance on the other side of the cable. I've been reading about jfet based piezo preamps and it's not uncommon to see people have 5 - 10 mohm input impedances on their piezo preamps.

1) How do I go about figuring out what the input impedance of my current circuit is?

2) How do I raise it if necessary?


texts:
I have a simple application: convert an automotive throttle 0-5V line to 0-2.5V on a circuit near (and feeding into) a fan controller. Very loose maximum frequency is 10Hz. I reduced R1 because the SA5.0A is potentially very leaky, but even with worst-case leak only 1% of Vin will be lost.
These component choices are largely because they're what I have on hand. I'm open to hearing more appropriate substitutes. One question mark will be maximum current required from the op-amp because I don't yet know what the input impedance of the fan controller is, so I'll have to measure that.

simulate this circuit – Schematic created using CircuitLab
Are there any typical automotive safety measures I'm missing?


texts: Three phase 230V input to single phase 5V/5W power supply

texts: How can I design a 5V/5W DC power supply derived from 3 phase 230V AC input supply? My application need to work, even if, only one phase is available.


texts: How to fix incorrect routing to SMD transistor terminals

texts:
I've got a doozy of a situation:

On this circuit I had made, I routed an IRL530N D2Pak transistor with Source and Gate switched....the large heat pad should be the gate input, but instead I routed it to ground.  Furthermore, I added 2 heatsink pads on either of the transistor, with traces from those pads going to the Gate pad.

To compound the issue, I added 11 small copper-plated through-holes on the Gate pad that runs through the board to the ground plane on the bottom side.  Unfortunately (for this situation), I added 2 inner layers (power and ground); those through-holes are part of the inner ground plane as well.

Here's a couple options I was going to take, all of which could possibly damage the board:

1) Heating issues may arise

a) flip the transistor 180 degrees
b) cut the Drain pin off
c) solder the Source pin to the square pad
d) cut the traces going to the heatsink pads
e) cut trace from the small right pad
f) bridge connection between heatsink pads and the 2 small pads
g) solder underneath of transistor (Gate) to 2 small pads (the left small pad will be the Gate trace
g) wire the non-SMD Drain pin that I cut off to the resistor to bridge that connection

2) May cause a short somewhere or I may accidentally end up removing the entire square pad (this would be my first time running this kind of procedure)

a) use a thin knife to cut around each hole (top and bottom of board) to break electrical connection
b) remove the parts of the copper off the top of the board
c) cut trace from small right pad, then wire it to ground
d) wire the square pad (now the Gate) to the pin that used to be connected to the right small pad
e) do nothing to the left small pad or the trace (would still be the correct route for the Drain)

3) Inner power and ground planes may short, or eventual re-soldering may flow through and come in contact with the inner planes

a) drill through each of the 11 holes
b) cut trace to right small pad, reroute to ground
c) route square Gate pad to the pin originally routed to right small pad

So far that's what I'm thinking of doing...I don't have enough expertise (or even a minimal understanding) of the cause-and-effect risks involved, so any opinion or alternative solution would be greatly appreciated.

If the board is a goner, let me know too...I only purchased 3 for a relatively cheap price, so I'll take the hit if that's the case.

Anthony


texts: Troubleshooting op-amp circuit and compactor for buzzer

texts:
I tried building a radiation detector (cheap photodiode Geiger counter) on perfboard:
http://opengeiger.de/StuttgarterGeigerleThruHole_en.pdf

More details here. With the circuit was turned on, without any photodiode excitation, in green are voltage readings:

The designer assumes a 1nA peak of the detector current impulse.

I connected the output of the second TL072 op-amp to a signal generator, then input 1 V peak. Nothing happened. I just want the speaker to work (datasheet). Any recommendations or things that stick out to you before I calculate, maybe simulate, if those are the correct values?


texts:
I have an application where I have multiple IR transmitters/receivers set up to read data.  These are removable and can be set up in a lab environment where I can control distance, light, etc.  I've been searching for a circuit that will let me measure signal strength of an IR transmission, whether it be through a Microcontroller such as an Arduino or through a scope.  However, all I see are people wanting to measure distance using IR.

My goal is to be able to take a brand new device(s) and get a signal strength baseline.  Then I want to compare older devices to that baseline to see if signal strength degrades over time.  Could anyone point me in a general direction?


texts: Getting 5VDC from 6V (4S 1.5V AA alkaline batteries)

texts:
For my current project, I need 5VDC rail to power an ATtiny85, an RF module, and an Ultra-sonic range sensor, all of which require 5V. 5V ensure that the ATtiny85 can be operated without crystal at the desired clock frequency reliably, and it also ensures sufficient range for the RF module etc. The total current draw expected, is about 50mA on average, and about 80mA peak.

Currently, I am considering powering the project using 4 AA (alkaline) batteries, in series to get a peak voltage of 6V. Keeping the project low-cost, in low volumes (say, 10 odd pcs), is one of the objectives. Would prefer to keep the batteries until their terminal voltage runs down to about 1.1V, i.e. for series connection, about 4.4V. Are buck-boost switching regulators the only option ?

Edit:
Reading around (arduino.cc forums) I found an alternative proposal, which seems to be low-cost and feasible, but would be good to have some community feedback anyway --

Use 3xAA alkaline (4.5V when new but down to 3.3V after run-down), with the DC-DC boost regulator like this one, selling for a what seems like a rather good price (within my project's budget). It can boost the inputs voltage between 1-5VDC, to 5VDC, supplying max current of 500mA (way more than sufficient for my needs). If this works, the only challenge is finding battery holder for 3 AA's. I've only seen those cylindrical, 3xAAA holders, but nothing for 3 AA's.


texts: How does a higher range when measuring current and voltage prevent burning of the fuse in multimeters?

texts: I have a question about digital multimeters. What happens when I initially set a higher range prior to measuring current/voltage in DC electric circuit? How does setting a higher range prevent burning of the fuse/ internal components?


texts:
We are doing battery heat testing and want to be able to vary the current in the circuit to different test points up to 100A. Our circuit schematic is attached. The MOSFET is IXFN360N10T. We attached the MOSFET to a piece of aluminum with thermal paste underneath. The circuit works extremely well below about 20A. A change of 0.01V at V1 causes a 1A change through out test battery. Vds is around 3.7V at max.

However, the MOSFET heats up significantly and smokes out. According to the SOA chart, we should be well within the safe operating range of the transistor. What is going on and what can be done to perform the test that we want?


texts:
I am working with arduino/raspberry pi modules and trying to secure them to a lego plate. Because of the soldering joints on the bottom, there isn't a flat surface to work with.

I have tried crazy glue which works. I also tried a sculpting clay which attempted to take care of the bumpy surface of the joints, but that didn't hold (the clay had crazy glue on both sides).

Even though the modules still worked, I would imagine that this introduces added resistance to the circuit where it wasn't intended.

It looks like standoffs are the best way to go, even though there is nothing readily available for this purpose.

I'm wondering if there are any other options to consider?


texts: Why is it that we use capacitors in Differentiator & Integrator circuits (comprising Op Amps) & not inductors?

texts: One of the possible reasonsI know is that capacitors are available in wide range of values and can be made more accurate than inductors. What other factor leads to the use of capacitors over inductors?


texts: Symbol for a potentiometer on a guitar amp layout diagram

texts: Was working to convert a guitar amp layout diagram to schematic and stumbled upon this component. Looks like a potentiometer but has some additional tabs on the front. The label reads "master". Anyone knows what I am dealing with?


texts: Help: need a compact shunt resistor for current measurement

texts:
I'm very new to electronics and learning as I am working on a project. I am trying to find a small compact replacement for the very large shunt that comes with a Current Meter I bought on ebay. Can anyone advise me on how to calculate an appropriate shunt resistor (ohms & power rating)?

These are the Current Meters I bought:
http://www.ebay.co.uk/itm/DC-50A-100V-Dual-LED-Digital-Voltmeter-Ammeter-Amp-Volt-Meter-Current-Shunt-/281587980311?pt=LH_DefaultDomain_3&hash=item418ff39817

I am wanting to measure the following...

Capacity in Battery-A  (Lipo 4000mAh 3s 11.1v)
Capacity in Battery-B  (Lipo 4000mAh 3s 11.1v)
Total draw of entire unit

I was hoping to achieve this with the 3 meters from eBay but my application only draws a small fraction of the current these meters can display.

My project is building a compact Ground Station (which is all contained in a suitcase being powered by 2x 11.1v Lipo 3 cell batteries with a SPDT toggle switch to flip between the power sources), and I think the power requirements of the system is up to 20 Watts. All this to run an FPV RC plane.

Can anyone help me out? I am hoping someone can suggest a suitable shunt replacement.

Thanks very much,
Nick.


texts: How can low voltage, high current (kA) power be dangerous?

texts: Aluminum refineries use electricity to separate aluminum from minerals it naturally occurs in. This electricity typically takes the form of low voltage DC ("low" meaning 4 to 6 volts), at very high current (on the order of tens of kiloamps). This much power poses an electrocution danger, but I don't understand how. If the entire electrical system runs at, say, 5 volts, and the human body acts like a resistor, then how can enough current actually make it through a human body to be dangerous? Similarly, how can an electrical arc through air happen, if it takes hundreds of volts to arc over a very short distance?


texts:
I have been trying to pass CAN frames between two different CAN busses using two different CAN channels on a STM32F746 MCU. The system always fails and freezes up in TX when it is supposed to be passing through CAN messages between the busses. The firmware shows the transmit messages are never clearing the CAN mailbox, which first pointed me to investigate TX. I have encountered some strange looking behavior on TX that I need help understanding.

Below is a basic schematic of the CAN bus system:

simulate this circuit – Schematic created using CircuitLab

The bus operates at 125kHz (8us bit time)
Bit timing is as follows:

Internal MCU clock of 216MhZ, prescaled down 54MHz for the CAN module
Time quanta Tq = 500ns
SEG1 = 13
SEG2 = 2
SJW = 1

In the following picture of TX and RX during operation, the system is not working as intended. RX looks healthy, but TX is supposed to be transmitting messages from the other bus. It is not. It appears to be ACKing however.

Next is a different capture from the same probing session. It gets weird! TX seems to jump in and fail in a way I don't understand.

Zooming in...

TX appears to be jumping in, maybe to ACK, but ends up truncating the end of the frame to shorten that last bit by over half of the normal 8us it should be. The last bit on RX is truncated to only 3.2us. TX then goes dominant for 4 or so bits inexplicably.

Finally, here is a zoomed in image of the 'normal' looking ACK from earlier. It also appears to be shortened to about 6.6us.

What could be causing this behavior?

I cannot figure out any mechanism which would lead to this type of error. Is it failing acknowledgments, arbitration, bit timing, something else, or a mix of all?

I have debugged the following:

The transceivers are good
The CAN bus signals all look healthy and square
I have tried different termination configurations and resistor values

I would greatly appreciate any insight or guidance on how to proceed with debugging from here.

Thank you!


texts: Best way to generate 26 Volts AC at 380-420Hz?

texts:
I have obtained a military vibrating-reed frequency meter that I would like to turn into an educational display unit, with a knob that adjusts the frequency from 380 to 420 Hertz, giving the user the ability to hear the frequency on a loudspeaker as well as see it in the frequency meter.

However, my experience is only with digital circuits like 74 logic, some BJT audio circuits, etc... have never generated AC myself before. How should I generate a 26 volt 400Hz signal?

I was thinking something like... Microntroller to generate a variable sine wave, which I would feed to an audio amplifier. One channel of the audio amplifier would go to a speaker and the other would go to a step-up transformer and then to the meter. Would that work?


texts:
Im trying to drive mosfet's gate with couple of BJTs: S9014 (npn) and S9015 (pnp). They are in half bridge, VCC is 12V. Here is schematic:

Input is PWM with frequency of ~70KHz from STM32 micro. I expect PWM from 0 to 12V on output, but strange thing happens instead: connecting 12V to VCC does almost nothing, PWM is still 0-3.3V with weird form and small DC offset (output was connected only to oscilloscope probe).
Question: Is my schematic correct and what is wrong with it?


texts: Can a unidirectional TVS diode leading to ground be replaced by a bidirectional one?

texts: I only have bidirectional TVS diodes at hand, can I use one of those instead of D1 (unidirectional) in the diagram?


texts: Generator shutdown on leading power factor

texts: I am having some issues in one of my projects. We have installed a generator in a building, where power factor is leading and -kvrs are shown on controller display. We know that this building is filled up with LED lights, due to which the genset controller orders a shutdown. We have consulted with a local vendor and he recommends installing a line reactor between genset and load. But even after installing this reactor still there is the same result. If you can help please give some suggestion.


texts:
Yes, I'm a noob. I am trying, please be nice.

I am trying to test the parts on an LED driver that's gone bad. Mainly because I actually NEED the thing to work, but also so I can learn how to do this sort of thing.

Mains in to a fuse (which is fine), then to this film capacitor. Multimeter on CAP setting gives me 125.5 nanofarads. (Why the meter doesn't auto-adjust to uF is yet another mystery, but that's another question.)

I can use the label info from the SIDE to find this document:
https://www.pcb-3d.com/wordpress/wp-content/uploads/CAPRR_EPCOS_B32921-B32926_SERIES.pdf

Below the legible printed info on the side there are only the 'reversed LR' symbols and the 'EN over EC' symbol.

On page 3 you'll find the match for the series, but showing 6 uF variations. None of the six values make sense to me as a match for what I measured with the multimeter.

I know that I am meant to use the info from the TOP label to figure out the proper farad value,  but for the life of me I can't figure out how to do that.

Some of it's obvious - 305V A/C. But the rest of the info doesn't seem to match the info in that doc? I am really confused by this.

If you can just tell me the value, great. That's enough to let me know if it's the .10 uF version and my .1255 uF actual measure is close  -  or if my actual measure is way off what it is supposed to be.

But if you can also explain how I'm meant to translate the label that'd be way better.

Phrased as proper questions:

What capacitance is the pictured capacitor?

AND

How does one use the text on the label to determine the capacitance?


texts: Could GaAs reflective-open SPDT be used as RF signal spliter?

texts:
In my schematics GaAs SPDT switch is used to feed two ICs in turn from single signal source. Switching between two signal destinations is made by applying opposite voltages to two SPDT control pins - A and B. According to datasheet voltages on control pins are always opposite - and it is obviously from typical reflective-short GaAs SPDT schematics (picture below).

But sometimes I need to feed two destinations of signal simultaneously. Could I use reflictive-open GaAs SPDT and apply equal ON-voltage to control pins (V1 and V2 at picture) to split input signal between outputs? In reflective-open SPDT Q3 and Q4 don't exist, so what could possibly go wrong?

If such using of SPDT is forbidden, how to solve this problem?


texts:
For an experiment (generating a travelling magnetic field) in high school I need a 3 phase current. My school does not have access to 3 phase power. Therefore I need to generate the 3 phase power out of the 1 phase 230 V Dutch standard.
A requirement is that the frequency of the voltage needs to be a sinus function and the functions needs to walk (1/3)period behind each other.
I red about a few ways to do this:

the Steinmetz circuit, but this doesn’t leads to 3 sinus functions.
use an 3 phase AC induction engine as a dynamo and literally generate a 3 phase current.

Are there other ways to create a 3 phase current out of a 1 phase current? All ideas are welcome!


texts:
What happens to the light bulbs if the power switch is connected. Will B shine brighter or will both? Or will nothing happen?

A & B are light bulbs.


texts: How to wire a Normally Open Button to a BeagleBone Black?

texts:
This one should be simple, but I'm fairly new to this.

The button has a COM and an NO terminal. Beaglebone pins can only take 6mA, so I don't have much room for error. My question is, how do I wire this and does it need voltage?

More information:

This button only has NO, COM. It doesn't have NC.
Here is the button.
http://www.adafruit.com/products/1185#Technical%20Details
There isn't any technical info listed that seems helpful.

Here are the pins:


texts: USB C connector design and resistor placement for USB 2.0 data cable

texts:
I have a follow-up question to this one.

I have a type C connector with 8 pins. No spec, type C female counterpart reveals G, Vcc, A2, A3, A6, A7. Remaining two pins do not respond to anything. G-Vcc shows 5.10V. A6-A7 shows 38 kOhm. G-A5/G-B5 on female counterpart shows 4.84V.

When using this to connect high-speed USB C device, system gives the following output:

[330114.311007] usb 3-2: new low-speed USB device number 61 using xhci_hcd
[330114.439054] usb 3-2: device descriptor read/64, error -71
[330114.675048] usb 3-2: device descriptor read/64, error -71
[330114.910996] usb 3-2: new low-speed USB device number 62 using xhci_hcd
[330115.039040] usb 3-2: device descriptor read/64, error -71
[330115.274963] usb 3-2: device descriptor read/64, error -71
[330115.382963] usb usb3-port2: attempt power cycle
[330116.034978] usb 3-2: new low-speed USB device number 63 using xhci_hcd
[330116.035567] usb 3-2: Device not responding to setup address.
[330116.243594] usb 3-2: Device not responding to setup address.

I'm new into this topic, and I've searched the available sources. Seems that the proper resistor is missing, but the problem is that I don't have an A5 pin! One of the tiny lanes on the plug itself does respond to A5, but why its pin is hidden by design? What could be done in this case?


texts: Are there any DIP alternatives to the FT232R?

texts:
I'm currently using an Arduino on a breadboard, interfacing with it via a FT232R chip mounted on a breakout board. For my final design I'd ideally like to use all thru-hole components for ease of construction (it'll all be hand soldered) but don't really want to solder the breakout board on (though if this is the only feasible way then so be it.)

Are there any thru-hole equivalents of the FT232R chip?


texts:
I have a prototype of an electronics product that is still in development. I know that if I were to sell my product that I would have to have it FCC tested before I could sell it. The thing is the product is still in development and I want to ensure product market fit before I run these in mass. I am also wanting to cash flow this project and being able to sell prototype devices or the "service of a prototype device to clients" will help me get the project off the ground without seeking investment before I need to.

I was wondering if any of you had done a similar thing and were able to sell your prototypes or the service of your prototypes to clients without the FCC testing, because your device was in prototype phase.


texts: I am trying to build a versioning system/repository for my Altium design project/files. Can anyone recommend a versioning system(preferably open source) for such files?


texts: negative base current in NPN transistor?

texts:
I'd like to create a simple circuit that makes an LED brighter depending on the amplitude of an audio signal. My idea is to use the following schematic ;

simulate this circuit – Schematic created using CircuitLab

My question is this - what happens when the voltage of the AC signal goes negative? Does any current flow out of the base of the transistor? And if so, what happens to the current through the transistor? Also, I appreciate that this isn't a great circuit to indicate the amplitude of the AC audio signal, but it should more or less work right?


texts:
I'm wanting to generate a VGA signal hopefully as painlessly as possible.

I have an odd question though. Everywhere I see that VGA requires a 25MHz clock for the sync signals.

Is it possible to just draw the screen slower? Like only refresh it at 30Hz? What would happen? I think CRTs would have more of a problem than LCDs. Would either of them work at a lower sync rate?


texts:
Is it possible to produce/obtain a metal halide (MH) bulb with the possibility to turn it off and on instantly - again and again? Most MH products require 30+ minutes to restrike.. Why is this?

Thanks


texts: Why isn't Ohm's law working for this simple circuit?

texts:
I have a 70W 12V-500V DC power converter, and something in these pictures is not adding up.

I run the 500V output through a high-voltage 332kΩ resistor.

Now, using the left multimeter I monitor the current through the circuit, and it runs up around 320mA.  Using the right multimeter I first check the voltage on the power supply leads: 511V.  (So right away we know something's off -- the supply isn't even getting warm after a few minutes of testing.)

Then I use the right multimeter to check the voltage across the resistor: 12V!

I verified the resistor's value with both meters.  If all of this is true then Ohm's law suggests that either the voltage across the resistor should be .320mA * 332kΩ = 106kV, or else the current through the circuit should be 511V / 332kΩ = 1.5mA.

(Of course the right multimeter itself is providing a path for current, but its resistance should be very high.  Indeed: when I remove the right multimeter from the circuit the current increases only 2-3mA.)

My best guess is that the output of the converter is not very smooth DC, or has some characteristic that is causing these multimeters to produce erroneous values.  If so, what characteristic might that be, and how can I adjust for it?

BTW, here's a close-up of the DC converter.  Maybe the design will be familiar to someone.

And in case the wiring isn't clear from the photos, here's how it was connected

simulate this circuit – Schematic created using CircuitLab

And here's some more information.  First, to remove all doubt, here's the resistor being measured after all this, so it does not appear to have fried.

And here is the whole shebang.  If the ammeter on the DC supply can be trusted, and this power converter doesn't have the ability to produce power out of thin air, then the true circuit current is under 3.6mA.  (This is consistent with the fact that I have observed no heat buildup on any component whatsoever.)  In which case the question is: Why is the Extech reading ~320mA?  If I switch the Extech to µA scale it reads around 3180 (still not right).  The other multimeter reads 0A at all scales, which is consistent with the voltage drop seen across the resistor (which implies 36µA true current).

Epilogue: I opened the Extech multimeter to find its 250mA fuse blown.  Replacing that made it behave normally.  Evidently it just has a very confusing failure mode!


texts: Why does USB only use 2 lines for RX, TX instead of multiple data lines?

texts: Wouldn't it be faster if there were multiple data lines (say 8) to transmit/receive data (say sequential bytes) instead of using a single line to transmit sequential bits?


texts: Avoid voltage feedback from laser psu to Arduino via pwm pin

texts: I have been using GRBL software on arduino board for quite a while now, however the only issue I have is that the CO2 laser PSU kind of passes a small current back to the Arduino from its control pins, enough to dimly light one of its leds.  This prevents the correct communication between PC and Arduino if the laser PSU is turned on first. Being a pwm pin, I dont know how to avoid this current feedback.


texts:
I want to drive a VCSEL with the MAX3795 driver, but this ship has a very complicated circuit on it pins.

Is there is another available driver with a simpler circuit that i can use ?


texts:
I am trying to using a USB-RS485 cable (which utilizes the FT323R). I have it configured to be all output, and to run in async bit bang mode.
I am only able to see data on my scope if I call the set Break on and set Break off right before each FT_Write Command. If I don't call those set Break On and Set Break Off, I can't see a differential on the wire.
Is there a reason for this? This seems wrong, am I configuring something wrong?
EDIT: Added Code!
#include <iostream>
#include <windows.h>
#include <stdio.h>
#include <ftd2xx.h>
#include <stdlib.h>
#include "string.h"
#include <unistd.h>

int main(int argc, char *argv[])
{
   uint32_t numDevs;
    FT_HANDLE FT_handle;
    FT_STATUS FT_status;    // status of the FT 232 chip

    //Open Device
    FT_STATUS ftStatus;
    char * value = "FT4T6TXN";
    ftStatus = FT_OpenEx(value,FT_OPEN_BY_SERIAL_NUMBER, &FT_handle);

    if(ftStatus == FT_OK){
        printf("successful open!\n");
    }else{
        printf("failure open! %d\n", ftStatus);
    }

    UCHAR Mask = 0xFF; //all output
    UCHAR Mode = 0x01; //Selects the Async Bit Bang Mode

    ftStatus = FT_SetBitMode(FT_handle,Mask,Mode);
    if (ftStatus == FT_OK) {
        // synchronous Bit bang Mode enabled
        printf("sync bit mode!\n");
    }
    else {
        // FT_SetBitMode FAILED!
        printf("setBitModeFailed!\n");
        return -1;
    }

    DWORD BaudRate;
    BaudRate = 366;
    FT_status  = FT_SetBaudRate(FT_handle,BaudRate);
    if(FT_status != FT_OK){
        printf("BAUD RATE SET FAILED! \n");
        return -1;
    }

    uint32_t bytesWritten = 0;
    UCHAR Buffer = 0x01;    // data to be written to the port

    //set flow control
    FT_status = FT_SetFlowControl(FT_handle, FT_FLOW_RTS_CTS, NULL, NULL);
    if(FT_status != FT_OK){
        printf("flow not okay\n");
    }

    //Begin Looping Inf
    while(true){
        //I was unable to see Data without calling this?

        FT_SetBreakOn(FT_handle);
        FT_SetBreakOff(FT_handle);

        //WRITE
        FT_status = FT_Write( FT_handle,      // handle to the chip
                        &Buffer,        // address of the data
                        sizeof(Buffer), // Size of the Buffer
                        &BytesWritten   // Number of bytes written
                    );

        sleep(1);

     if(FT_status != FT_OK){
         printf("write not successful! %d \n", FT_status);
     }

    }
   FT_Close(FT_handle); // Close the Serial port connection
}


texts:
Johnson–Nyquist Noise increases with resistance - so does it become infinite for an open circuit? Specifically why is the input to an oscilloscope that is not connected to anything not completely saturated by Johnson–Nyquist Noise (assuming the resistance through air from oscilloscope input to GND is near infinite).

Johnson–Nyquist Noise Equation from Wikipedia:


texts:
I am having some problems with my code, and understandning what my warnings are trying to say to me..

These are the warnings i get

WARNING:Xst:737 - Found 4-bit latch for signal <counter_10>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:737 - Found 4-bit latch for signal <counter_1>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:737 - Found 1-bit latch for signal <ret>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:2677 - Node <Sreg_FSM_FFd1> of sequential type is unconnected in block <game>.
WARNING:Xst:2677 - Node <Sreg3_FSM_FFd1> of sequential type is unconnected in block <game>.
WARNING:Xst:2677 - Node <Sreg2_FSM_FFd1> of sequential type is unconnected in block <game>.
WARNING:Xst:2677 - Node <Sreg1_FSM_FFd1> of sequential type is unconnected in block <game>.
WARNING:PhysDesignRules:372 - Gated clock. Clock net
   segment2/counter_1_cmp_eq0000 is sourced by a combinatorial pin. This is not
   good design practice. Use the CE pin to control the loading of data into the
   flip-flop.
WARNING:PhysDesignRules:372 - Gated clock. Clock net segment2/counter_10_and0000
   is sourced by a combinatorial pin. This is not good design practice. Use the
   CE pin to control the loading of data into the flip-flop.
WARNING:Route:455 - CLK Net:segment2/ret may have excessive skew because
WARNING:Route:455 - CLK Net:segment2/counter_1_cmp_eq0000 may have excessive skew because
WARNING:Route:455 - CLK Net:segment2/counter_10_and0000 may have excessive skew because
WARNING:PhysDesignRules:372 - Gated clock. Clock net
   segment2/counter_1_cmp_eq0000 is sourced by a combinatorial pin. This is not
   good design practice. Use the CE pin to control the loading of data into the
   flip-flop.
WARNING:PhysDesignRules:372 - Gated clock. Clock net segment2/counter_10_and0000
   is sourced by a combinatorial pin. This is not good design practice. Use the
   CE pin to control the loading of data into the flip-flop.

And my code looks like this
https://www.dropbox.com/s/9lytyrdn9f4mh1b/randomnumber_medGame.rar

I would be very grate if someone could point out what the problem is.

A huge problem is when test changes value in one module, the other module shall react on it, but the segment doesn't show the right combination which irretates me alot.


texts:
In a basic circuit, does making a transformation of voltage source to current source affect the power output of the source? I'm being asked to find the power output of a voltage source and then to confirm that power output by doing a source transformation to a current source. I ask this because the power output is different once i have realized the transformation and i'm very confused about that.
By basic circuit i mean the one below. The power output is different in each case and i can't get why. Isn't it supposed that both circuit are equivalent? If that so, how come the power output of the source is different in each case

Power output for Voltage source 39.94kW and
Power output for Current source 59.91W.

I'm sorry if the question is dumb.


texts:
simulate this circuit – Schematic created using CircuitLab

My question is about elementary series current calculations. Above you see 3 circuits. All circuits have a Vin of 24v connected to either 1 or 2 heating elements (Z1 and Z2).

When calculating the current in circuit 1 I apply the formula I = P_Z1/U_Z1 = 2W/12V = 0.17A.

When calculating the current in circuit 2 I apply the formula I = P_Z2/U_Z2, 1W/12V = 0.08A.

When calculating the current in circuit 3 I apply the formula I = P_tot/Vin, 3W/24V = 0.125A.

OR

I can calculate I in circuit 3 by first calculating R_tot = R_Z1 + R_Z2 then using I= Vin/R_tot.

R_1 = U_z1²/P_z1 = 12²/2 =24 Ohm.

R_2 = U_z2²/P_z2 = 12²/1 = 144 Ohm.

So R_tot= 168 Ohm. with I = 24/168= 0.14A.

Question 1: How come I get 2 different answers when applying the 2 different ways to calculate I? Where am I going wrong here? AND which answer is the correct one?

Question 2: In circuit 1 (and 2) I connected a 12V  heating element to a 24V power supply and calculated I throug 2W/12v = 0.17A. I get the feeling that this is wrong because the source voltage is not taken into acocunt here, where am I going wrong here?

Question 3: what does it practically mean when connecting a 12V/2W element to a 24V source?

Question 4: In circuit 3 we have I = 0.14A. this means for Z1 (and Z2) that P has changed? P_z = 12V*0.14A= 1.68W, but when we started it was 2W. Where Am I going wrong here?


texts:
today I learn about latency especially Tpdhl (high to low) and Tpdlh (low to high).
My question is, let's suppose a gate has Tpdhl=8 and Tpdlh=6 so how much time it will take to process the input if it was uninitialised at first?
Does that rely on the input if it's 0 or 1? please help me


texts: Would this USB detection circuit work as expected?

texts:
What I am trying to achieve is detect from MCU, whenever FTDI(FT232R) chip is connected to USB(not enumerated, just powered up from USB).

When ONLY USB is connected, MCU will get his power supply from +5V bus and will detect on (B) pin that USB is connected.
When ONLY VR will supply power to circuit, then MCU again will get power from +5V bus, but FTDI will ONLY get VCCIO. On middle of voltage divider R10/R11 I expect there will be 0 and MCU will not detect USB connection on (B).

The question is - would it work the way I described or I missed something? My concern is it ok to hook up only VCCIO to FTDI? Would it damage or lead to unknown behavior?

UPDATE:

I have slightly modified circuit, so VCC is connected to VCCIO.

or

Would this do the job?


texts: Difference between RFCOMM and L2CAP Protocol in Bluetooth Communication

texts:
I just started learning the essentials of Bluetooth Programming since it is heavily used in my project.

I have an nRF52 Development Board and a Raspberry Pi 3 - Model B (with built-in bluetooth). I want to make the 2 devices communicate with one another for now for prototype development (e.g., Exchange single bytes of data).

In section 1.2.1 Choosing a communication partner of a useful PDF that I have come across: (https://people.csail.mit.edu/rudolph/Teaching/Articles/BTBook-march.pdf), it introduced 2 transport protocols:

RFCOMM
L2CAP

I want to know the main comparison points between the two so I may be able to decide which of them is the suitable protocol to be used. The resource above, of course, stated important information about the two but as a novice bluetooth developer, I may not able to visualize them that much.

Can anyone compare and contrast the two? Thank you in advance.


texts: Is possible compute the bandwidth of a Narrowband Twin-T Passive Notch Filter?

texts: Exist any function of R and C, for calculate f1 and f2 at figure below?


texts: Calculating forward voltage for a string of fairy lights: multimeter shows "1"

texts:
I'm trying to provide a USB power source to a string of fairy lights that look like these.

They all appear to run in parallel, connected horizontally along two wires until the last led.

I tried isolating a single led to calculate the forward voltage drop, but my multimeter shows "1" with the diode test, and successfully lights up the LED. Any other range fails to light the LED, and also shows "1".

Am I going about this the right way? I'm still confused about the difference in being able to supply current, and drawing current. I know a USB can provide 100mA, but there's no specification for a battery except for mAh?

How can I figure out an appropriate resistor, or at least calculate the forward voltage drop?

The waterfall analogy doesn't seem to be working for me...

Can I just assume it's 3 volts because it's in parallel?


texts: Best interface to read voltage signal on PC?

texts: I have a device that generates a 6.2 vdc pulse (from 0 vdc) periodically and would like to store the time between pulses with microsecond resolution. I don't care what the length of the signal is, just need to record the time when the signal goes high. Is there an OTS interface I can use for this, or can someone suggest a good approach for capturing this data, Arduino etc? TIA.


texts: Why doesn't the 'V' curve of a synchronous motor touch the D.C. field current axis?

texts:
Why doesn't the synchronous motor armature current become zero with a field excitation change?

It can be seen from 'V' curve.


texts:
I'm trying to use the __delay_ms() function to make an LED blink on the PIC16F77A.

The reason I think it stalls on the __delay_ms() function is because whatever I set RB0 to before the delay function always works, while anything after it doesn't (for any value I pass in).

I'm using a PICKit3 and MPLAB X to program my board. I have a 10k pullup on MCLR and a 16MHz oscillator with two 22pF capacitors in parallel on pins 13 and 14 of the PIC, and RB3/PGM wired to ground (basically the same setup as in this tutorial). I've also tried this with a 20MHz oscillator (with 22pF and 33pF capacitors, as specified in the datasheet).

#include <xc.h>

// BEGIN CONFIG
#pragma config FOSC = HS        // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF        // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF        // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)
//END CONFIG

#define _XTAL_FREQ 16000000

void main()
{
    TRISB0 = 0; //RB0 as Output PIN
    while(1) {
        RB0 = 0;
        __delay_ms(1000);
        RB0 = 1;
        __delay_ms(1000);
    }
}


texts: Single battery, charger and power supply?

texts:
I have a small backup battery (7Ah SLA for now, but probably a 130Ah flooded cell outside later) for my two in-house transceivers and two things that could potentially charge this battery: a 30A 13.8V linear power supply and a small 0.5A Battery Tender trickle charger. Right now, I have my HF radio plugged into the 30A PSU and my VHF radio plugged into the Battery Tender and the battery with a simple Y cable I made. This seems to work, but it has the downside that any use of the radio (7-15A draw) drains the battery fairly quickly as the draw is an order of magnitude higher than the charge rate.

I'd like to wire all of these devices into a common circuit.

Three and a half related questions:

Recognizing that the Battery Tender is likely to see the power supply's output as a fully charged battery and shut off whenever the power supply is running, is there any obvious problem with having two sources of approximately the same voltage on the same circuit?
Since this would be in parallel, the battery would still end up providing some (half?) of the current to drive the radios when they're used, right?
As far as I know, car batteries are charged by simply throwing 13.8V at them from the alternator with no attempt made to reduce available current once the battery is charged. Can I just charge the battery with the power supply by simply having them in the same circuit? If the power supply is on but not powered, is it possible that it might accidentally provide 120V back into my wall socket?


texts: RMS calculation of signal with high crest factor up to 10 MHz

texts:
I'm attempting to measure the RMS of an AC signal with a crest factor of up to 10, at frequencies of up to 10 MHz. From my brief research I can see many ICs that work well above 100 MHz (designed for RF stuff) and many that work below 1 MHz. I can't seem to find any IC that works in the range I need.

Would a DSP be a good solution to this problem? What sort of frequency does the DSP need to run at to accurately measure my 10 MHz signal? I can't find any simple information telling me this sort of thing and I wanted to know how possible it is before I start any in depth reading, since I know next to nothing about DSPs right now.

Thanks.

Edit: LTC1968 is about he closest I can find, but it specifies crest factors of less than 5, and it's 3dB error bandwidth is 15MHz, which is a little close to my 10 Mhz requirement, but I think I can combine it with an RF chip


texts: I2C data line not having correct voltage levels

texts:
I've been working on a project with a EFM8UB1 development board and ATECC508 I2C peripheral.  Everything works fine but I'm having problems with I2C when moving to a PCB.

Here is a trace of the clock

Here is a trace of data

My scope isn't very good but notice that the voltage levels for data are incorrect.  It's not fully driving logic 0 low.

Here is an excerpt from my schematic:

I'm not sure what to do or what could be causing the problem.  Does anyone know of something that could be causing the issue?

Microcontroller Datasheet

I2C Peripherial Summary

**Update

Turns out the problem was because I mislabeled the pins on a PCB footprint early on in the project.  Thanks for the feedback and suggestions.


texts: Communication over DC Bus at low data rate

texts:
I am looking for a solution to modulate a data signal into a DC powerline that has 12-60V.
I found for example the DC-Bus solution from Yamar. But they are the only ones offering this and their chips are 5$+; even in high quantities. That's too much.

I read somewhere that I could use a coupling capacitor. But then I whoud still need to know how to it like that and how I modulate it best (I know what a coupling cap is tho; even tho I don't really get how I would do that yet)

If there is an easy and cheap solution to implement without a full IC, I am glad to hear about it too :)

Any advice is appreciated, even if it's just Kewords I can google about.

The data rate should be in the kbps range. Mbps is nice but by no means needed!

And yes, there is really only that way of doing it. RF is no option and additional wires too.

Edit1:

The data I want to transmit is a voltage of a solar panel every few seconds. So as you can see, the data is not very vital and if I wanted to increase reliability I could just transmit the voltage twice.

Because multiple panels are in series , I thought of a master that announces which panel can "speak" next.

I thought maybe it's easiest if there is like two different frequency levels. one for the master to say whos turn it is and one for the actual voltage. So e.g: base indicating frequency is 100khz. Each khz more is +1. so if the master modulates in 100kz that means panel 0 should speak, 101khz means panel 1 etc.
Same would go for VTG: base frequency could be 10khz and each additional khz could means +1. so eg. 12V is 10khz, 13V is 11khz etc.

I don't know how stupid or difficult that actually is compared to serial methods :)

I used RS232 for a lot of projects yet even tho I wouldn't say I understand the protocol itself to it's farest extents. I would say I know the basics (+3 is logical zero, -3 is logical 1, There is a start bit synchronizing the clock and a stop bit I don't understand exactly what it is for other than a minimum of one bit pause between two bytes :).

Thanks in Advance!


texts:
What is relation between CMSIS libs released by ARM.com, libraries provided by manufacture  and GCC ARM libraries ?

What is the exact purpose of each? Which of them Should I use?


texts: I´m doing a parasitic draw test on my car battery, in order to check the draw with the car locked and alarmed I need to use the COM and 20a sockets of the Multimeter, if I use the COM and mA sockets the battery doesnt make a circuit (car dead).  Whats the mA reading on the Multimeter, 240 mA??


texts:
Many of the cheaper lighter adapter plugs do not come with screws for connecting the wires to them, but rather with just the bare metallic contacts - to which I am supposed to do what, solder the plus and minus wires in such a vibration rich environment ?

edit

Here is an image of the terminals that I was talking about:


texts: Why does an inverter circuit (NOT gate) need both a transistor and a complmentary transistor?

texts:
While reviewing logic gates, I read that to make an inverter circuit, you need two transitors, one of which is complementary, like so:

Assuming the intention of this circuit is to produce a NOT gate, then I ask:
Is the lower transistor necessary? Without it, it appears to me that the circuit would function just fine as a NOT gate.  If it is not necessary, is there a situation where it would be useful to have a second transitor?


texts:
I'm trying to cross check mathematically the mA being discharged from a .33uF capacitor which is charged to about 1200V by a circuit

which is provided 37W of power to it. I do it three ways.

1) The circuit draws 35W total. 13V @ 5A = 65W. But the power supply drops the 13V to 7V to maintain the 5A so the effective wattage is 7V x 5A = 35W. I just assumed this 35W carries through the entire circuit and out T2 because energy cannot be created and destroyed and there is little to no resistance from what I can see. So the wattage coming out of the capacitor is still roughly < 35W. We should use Vavg I think, not Vpeak, so 35W / 600Vavg = 58mA.

2) Now (1) makes sense, but I was hoping there was a cross check. I noticed on a page like this: http://cnx.org/content/m42427/latest/?collection=col11406/latest (see Example 2) you can calculate the mA from a capacitor via it's reactance. X = 1 / (2 x Pi x freq x C). As shown there I do the same. I put the gas discharge tube on the scope

\$X_C = \dfrac{1}{2\pi f C} = \dfrac{1}{6.28318 × 42 ×  330\cdot 10^{-9}} = 11483 \Omega\$

720Vrms / 11483 = 0.06270A or 62mA Great, this works. Essentially the same as (1). So (1) and (2) validate each other. This also means the wattage then is 720Vrms x .0627 = 45W. 45W is a little too high and not valid I think. After all Vrms is for AC, I have changing DC. So if we used Vavg its 600/11483 = 52mA, 52mA x 600Vavg = 31W. This makes more sense and probably also accounts for the wattage loss from stepping up the voltage @ T1. (35W - 31W = 4W loss).

3) But then I found E = (V² x C) / 2 which is used to calculate the energy per pulse from a capacitor discharge. Also conveniently calculated at: http://www.vishay.com/resistors/pulse-energy-calculator/ E = (1200Vpeak² x 0.00000033) / 2 E = .2376 Joules per pulse Joules per second = .2376 x frequency Joules per second = .2376 x 42.4Hz Joules per second = 10.07. Joules per second is the same as watts. Watts = 10W. This is shown easily and proven with the Vishay pulse calculator at that URL above.  10W? Why the sudden massive drop in wattage?

So this is where I am right now, I want to know why (3) is only giving me 10W. How can 1 and 2 work out, but 3 be so far off. Is (3) not an applicable formula to use in this case?


texts: Transistor with emitter attached to another transistor's base

texts:
I made a circuit that looks something like this:

simulate this circuit – Schematic created using CircuitLab

If I touch the loose wire with my finger, the LED will light up. Could someone explain what is going on? Is there a specific name for this effect?


texts: Can I use stall detection as my only obstacle detection or will that damage the DC motors over time?

texts: I plan to build a robot that is likely to bump into a lot of things quite often. I know I can detect if a motor has stalled by measuring the amps it is pulling and would like to use that as a simple way to detect any collisions, but I'm worried that this might damage the motors if used a lot. Can this be applied safely without harming the motors over time?


texts: Italic or upgright font for circuit components

texts:
Should one italicize symbols used to represent electronic components in a circuit diagram?

Some context:

According to NIST, typefaces for symbols should be italic if they represent a quantity or variable. The problem I see is that sometimes this is the case and sometimes it isn't.

For example, a resistor could be represented as "R1" and represents a quantity, namely the resistance of that particular resistor and hence, it should be italicized. In an accompanying text you could write "R1 = 1 kOhm" However, a transistor could be represented as Q1, but does not represent a single quantity, but rather the type of component used or multiple quantities. The quantities associated with it could be printed alongside it, such as "W/L = 360/2000 nm" in case of a MOSFET or "Beta = 400 in case of a BJT". Hence, I feel that it shouldn't be italicized, since you wouldn't write "M1 = 360/2000 nm". But I also feel that it is inconsistent to italicize some types of components and not other types.

So in summary, I can think of 3 ways to do it: (feel free to suggest other ways)

Italicize everything -- Problem: "wrong" style for transistors
Italicize nothing -- Problem: "wrong" style for resistors
Only italicize the components that can be represented by a single quantity -- Problem: inconsistent style between components

So which is the "correct" way to do it for example in scientific publications? (or in any situation)


texts: When finding impedance of an RC circuit, why do you multiply with -j and not j?

texts:
I understand the concept that the voltage lags behind the current in a capacitor, which is why we have to use imaginary numbers to find the impedance of a simple Series RC-circuit like this:

Which gives the following vector diagram:

What i dont understand, however, is why you have to multiply by -j and not j when calculating the capacative reactance. Based of my limited understanding of the complex plane and rotation, multiplying by j would rotate the reactance 90 degrees counter-clockwise, bringing it in phase with the regular resistance. How come this is not the case?


texts: Motor control with an Arduino Uno... Is it possible (and safe)?

texts:
I have an Arduino Uno and an inexpensive RC jeep with a functional DC motor and front-wheel turning servo, but I don't have an Ardumoto shield to control it (yet).

I'd really like to learn if it's possible and safe for my Arduino Uno (from back-EMF) to build a circuit to control it with the Arduino Uno, using some switching mechanism to power the motor separately from the Arduino Uno's 5 V.

I discovered the motor takes (I believe) a maximum of 6.8 V by connecting it to a 9 V battery (its label says it takes 9.6 V for the entire vehicle, including the front wheel servo and some LEDs). I connected the battery via my breadboard with an SPST mini switch and read the voltage with my meter. The motor has 8 ohms of resistance, so I figure it's pulling 0.85 A / 5.78 W.

I have some 741 and LM324 op-amps, some 1N4001 and Zener diodes, a variety of NPN and PNP transistors, including some TIP120 Darlington transistors, and several capacitors.

Could I use some combination of them to power the motor and servo while protecting the Arduino Uno from back-EMF? If not, I will order the Ardumoto.

If it helps, pictures of the jeep with tagged closeups of the stock motor/servo controller are here:

http://www.flickr.com/photos/tommytwoeyes/sets/72157627827980121/

I've googled this extensively and also asked about it on Reddit. No disrespect to those guys, because their answers were awesome. But there was so much information between various sites and different posts on the subreddit, that it was a bit overwhelming and occasionally conflicting. I am just trying to learn and identify the best solution.


texts:
I have been wondering if I have for example to calculate one sum and a multiplication, I would have two different states, and if so, how would my truth table be, for example if I have a register tot to store the distance, and it's given by:
$$D = L\cdot K + f$$
For an arbitrary function, I would like to know if I would have to include one state for calculating the product $$LK$$
and another to solve the sum with f.
Any explanation would be great.


texts:
It is good practice to ensure some design margin for the electronic circuit in terms of absolute maximum ratings.

What is the proper way of selecting such a margin for Total Power Dissipation?

Let's assume 20% as a safety margin for any reason and SOT363 NPN Transistor as an example:

On the chart below there is a common power derating curve for BC847 NPN Transistor in SOT363 Package - [Blue].

I calculated the -20% Power alternative [Green] it looks good however the closer we get to the Absolute Maximum Temperature Rating [150C] the smaller the margin becomes. This is why I wonder if it is a proper way of doing this?

As an alternative, I added another line which is basically -10C of the base the value [Green].

Is there a way to define something "in-between"?


texts: How can I seal a temperature sensor against water?

texts:
I have some DS18B20temperature sensors around and was wondering how can I seal them and use them in a water tank. The sensor must include a small resistance (140 k or so).

Is there a simple DIY way to do it? it need to be something with a small thermal resistance/capacity.


texts: What sort of op amp could I use for low frequency sound application?

texts:
What categories of op amp would be best for a driver circuit that drives 8 ohm DC speakers at low frequencies  (under 500 Hz) but is battery powered (no more than 6V DC)? The waveform doesn't have to be smooth so even a class D would be fine.
1W power draw is fine.

Should I be looking for a high impedance / high gain or some other features?


texts:
I have seen this type of electric lighter :
But I don't really understand why the electric arcs are crossing each other instead of going straight.How is it possible?


texts:
Please see the following code. (For the sake of clarity, it is a YCbCr 4:2:2 to 4:4:4 SerDes.)

always @(posedge clk_54, posedge reset) begin
if (reset)
    cntr <= 0;
else if (flag_in)
    cntr <= cntr+1;
end

always @(posedge clk_54, posedge reset) begin
if (reset) begin
    Y  <= 0;
    Cb <= 0;
    Cr <= 0; end
if (cntr==0)
    Cb <= YCbCr;
else if ((cntr==1)||(cntr==3))
    Y <= YCbCr;
else if (cntr==2)
    Cr <= YCbCr;
end

The input clock is 54 MHz. cntr is a two bit counter. flag_in is a flag telling the counter when to start. It is very clear than none of the three output signals, Y, Cb, or Cr, change at a faster rate than 27 MHz (half of 54). If so, can I safely sample the signals at 27 MHz and not worry about clock domain crossing issues, setup and hold, etc?

I plan on synthesizing with Vivado and placing onto an FPGA. The 27 MHz clock will be derived from the 54 Mhz with Vivado clocking wizard.


texts: What is it that strips vocals from audio when a 1/8" audio jack is partially unplugged?

texts:
Every once in a while, my eighth-inch audio jack will slip loose and I'll seemingly lose only the voice part of a track -- leaving somewhat of a "karaoke" version. What I would guess about how audio plugs work suggests that I'd be making this up; however, I've asked and others tell me they've experienced this as well.

What causes this stripped vocals from audio when a 1/8" audio jack is partially unplugged?


texts: What does "realize SoP function using gates with arbitrary number of inputs" mean?

texts:
I am confused what "gates with arbitrary number of inputs" mean. If we are asked to realize function SoP(0,2,3,6) using standard truth table using gates with arbitrary number of inputs... how is it different from standard boolean expression( after simplification from full sum of minterms):
$$x_1'x_3' + x_1'x_2 + x_2x_3'$$

This can be realized as follows:

simulate this circuit – Schematic created using CircuitLab

BUT, problem says to realize SoP(0,2,3,6) with gates of arbitrary number of inputs...
I am not sure what to do with it.
Need help!
Thanks


texts:
I'm reading "The Art of Electronics" (3rd edition) by Paul Horowitz and Winfield Hill. In the 2nd chapter on BJT (page No. 79, section Emitter follower). The author says:

  ".. In general, the loading effect of the following stage causes a
  reduction of signal. For this reason, it is usually best to keep Zout
  << Zin (a factor of 10 is a comfortable rule of thumb)."

Here Zin and Zout are the input and output impedance os an emitter follower circuit.

My question is, isn't it desirable to keep output impedance more than the input impedance to prevent loading effects? For example, consider the following:

If RL << R2, the equivalent resistance of the lower part of the divider would go down and hence there would be a reduction in Vout with the load. Can anyone please explain what am I missing here? Thanks for your help.


texts: Am planning to build a odometry speed sensor based on optiflow to measure the speed of the conveyor. I am using ADNS-5020-E from a old mouse of mine and managed to get the X and Y coordinates by interfacing it with my arduino, the problem am facing is to convert this x coordinates into speed.


texts: From Where Comes the Second Name in a Label in an Eagle Schema

texts:
I created a schema in Eagle and named some nets "BEAT_1", "BEAT_2", "BEAT_3", etc. But after adding labels to this nets, there is a second name in the label "BEAT_1/2.2A".

From where comes the "2.2A" part of the name?

How can I get rid of this second name?


texts:
I've been trying to solve a problem, but a few days of searching has yielded nothing, and I'm inexperienced to create my own electronic circuit. First, let me explain the problem. We use data acquired (hijacked) with the monitor in our control loop to send setpoints to the source whose feedback must be connected to the sink (they are both from the same OEM, and this connection is "crucial").

We can log feedback from the source by connecting the OEMs diagnostic tool and compare it to the feedback we measure by monitor. We noticed that when both Sink and Monitor are connected, an additional dynamic is introduced into the signal measured by the monitor with tau being up to 0.2 - 0.3 seconds. This dynamic disappears if we connect only monitor to the source (but the system doesn't work if the sink has no feedback).
My idea for this problem was to split the signal with either operational amplifiers or optocouplers. But I don't even know where to start, let alone choose the correct components, and I believe my initial ideas are very naive. For example, a wire going from source to sink to pass through an optocoupler to copy the signal for the monitor, or, copy signal twice (we have 24V and 12V in the system, and if something like this is plausible, I know we need to add resistors to divide the voltage for it to be 0-10V):

Am I on the right track? Are there ICs that can simplify this, or even solve it out of the box? What would be the best solution?
EDIT: additional info about the time scale. Here is a plot of measured values from the left case in the first picture. The red full line is a setpoint we've sent to the source, the blue dotted line is setpoint he is receiving, yellow dotted is the feedback he is sending, and the purple full line is the raw feedback we measure with the monitor (no LP filter, only scaled from raw voltage to deg). Logged data by OEMs tool has a small and variable sample rate, with the lowest sample time being 100ms; our sample rate is 62.5Hz. Timestamps are synced by hand, so dotted and full lines may be off by a few ms.


texts: Is it possible to measure and log temperature using a microphone port of PC?

texts:
Instead of using an expensive logger, I'd like to measure and log temperature using a PC microphone port.

I'm going to use TMP36 Temperature Sensor. The output voltage of the sensor is measured by the mic port. The voltage is supplied from a USB port.

Here is the diagram.

But here are my concerns:

the mic port might have a certain range of voltage it can measure
the accuracy of voltage the port can measure might be impractical
Windows might not have the feature to measure the voltage directly

Is it possible?

EDIT 2018-02-14 9:36

My huge misunderstanding was the mic port can measure any kind of voltage generated by a mic to detect sound. Here are what I learned from the comments and answers.

The mic port will likely be AC-coupled (i.e. for AC signals only)
There might be other obstacles (e.g. low frequency cut)
So what I planned is hardly feasible
To measure voltage by a mic port, you need to build a certain circuit or use a frequency converter
It might be better to take other options such as Arduino Nano clones(~$3.50 on eBay)


texts: Hybrid Track vs. Conductive Plastic Lin. Potentiometer Resistive Element?

texts:
I'm playing around with developing a homemade linear potentiometer for a project (and for fun), and I'm stuck wondering: what is the advantage of using a hybrid track design (conductive plastic over a wirewound element) vs simply a conductive plastic as the resistive element?

Assuming the plastic is evenly conductive across it's entire length, with the goal being good linearity, does the hybrid design give any sort of added benefit?


texts: How can energy "physically" be fed back into the grid?

texts:
I have found some similar questions (below), but I am still having issues understanding what is "physically" happening when energy is "fed back into the grid" and the equipment necessary for this.

What happens to excess energy fed into the power grid?
Staying in Phase On The Grid
Feeding energy to the power grid
Is there a minimum amount of electricity that can be fed back into the grid?

My question seems to have multiple parts, but I believe they are needed to understand the bigger concept that I want to comprehend. Please correct me if I am looking at this wrong, or I need to clarify something.
How does this physically happen?
The way I see it is that a utility is able to send 3 phase electricity over multiple lines, for example, 1 phase per line, for a 3 phase power supply. Most homes only need one phase, and therefore one line entering the home. But if electricity is traveling in AC form over long distance, wouldn't feeding the excess energy of a home (produced by PV) back into the one phase line that is entering the home then potentially cancel out the frequency of the energy coming into the home?
I cannot comprehend how, for example, multiple homes can feed their excess photo-voltaic energy (PV) into a grid using the lines of the public utility. To me it would seem there would have to be a dedicated "feed in" line where a home puts its excess PV energy back into the grid, and that this line would be shared by multiple homes, however, only one home could use it at a time, so that the proper phase and frequencies are maintained and congestion avoided.
Equipment
Another issue is that PVs are outputting DC, so an inverter would be necessary to convert the electricity to AC for the energy to then be able to go back into the grid. Can excess PV be fed directly into the grid using an inverter? Or is it necessary to go through a "middle man" like a battery, and from there the DC can be converted to AC.
Another issue is me wanting to know all the equipment required to do this. The minimum equipment I believe is necessary to feed energy back into the grid:

PV panels (Or any form of a distributed energy resource (DER))
Inverters (Convert PV panel DC to AC)
Transformers (To step up the voltage to be sent back into the grid)
Some sort of switch to determine if energy is going into the home, or back into the grid
Battery (to work as a "middle man", or possibly deal with imbalances and smoothing)

What is a utility doing with this excess home energy?
Is the utility automatically distributing the excess energy from individual homes to other loads in the grid? Are they "bleeding" it off somewhere similar to a pressure valve in cases where they cannot handle all of it?
Another issue is there are multiple power producers that are using lines that stretch hundreds of miles, and now you have homes feeding energy back into these lines, so I am guessing that a single power producer needs to be in charge of an entire section, so there is no congestion.
I attached a figure of how I am imaging a small section of the grid where the homes are “feeding” energy back into the grid. Right now I only have the loads, substations, and power producer, but my hope is after getting answers to my question I may be able to add all the pieces necessary to help visualize the process.

If someone can point me to some sources with diagrams and equations, then perhaps that may help me with my questions. Please let me know if more clarification is needed.


texts: Strange and contradictory AGC characteristics in datasheet

texts:
I am trying to select an IR receiver for a remote controlled unit, from this table. Here is one example, but all of the parts exhibit the same seemingly contradictory specification.

Having a look inside TSOP75438's datasheet, we immediately notice the promising:

  IR Receiver Modules for Remote Control Systems
  Recommended for NEC code: yes

Cool. However, moments later, there is:

  For bursts greater than:                                     70 cycles
  a minimum gap time in the data stream is needed of:          4 x burst length

Hmmm. Here is a NEC example message:

With carrier frequency 38kHz, the initial 9ms pulse consists of 342 impulses, much more than 70, and the pause of 4.5 ms is much less than 4*9 ms.

Here is some more data, from an application note:

Note that 70 cycles @ 38kHz equals approximately 1.8 ms.

I understand that the above restriction is posed by the Automatic Gain Control unit, in order to distinguish between data and long monotonous sequences of IR noise form e.g. fluorescent lamp or LED backlight. However, my understanding MUST be flawed, as 1) the part is actually recommended for this protocol and 2) I just tested it with a scope and it works perfectly.

So what am I missing?


texts: KiCAD 5 --- what is the significance of the various GND symbols?

texts:
I'm new to KiCAD. I see symbols for GND, GNDA (analog), GNDD (digital), GNDPWR, GNDREF, etc.

Is there any significance aside from "schematic documentation"?

I was expecting that maybe the reason for the multiple symbols is that the PCB layout tool can use those to somehow enforce separation of ground planes?  But it instead seems buggy in the sense that not only the ratsnets connect GNDDs and GNDAs together:  in the PCB, it actually renames all the GNDD pads to GNDA !!!

Am I missing something, or doing something wrong?


texts:
I will soon need to build multiple boards where I will solder a DUT, to... Test it.

In order to speed up test time, we are working on a multi board approach: each board will feature four connectors, north, south, west and east, and you can connect many boards together, just like puzzle pieces.

We will have one additional mother board, that will be connected to one of the edges, free connectors. The mother board should be able to select and activate one daughter board at a time.

Pretty picture:

What I need is a "board enable" signal, separate for each daughter board. On each daughter board we will have a somewhat smart support chip, it is basically an I2C slave, the motherboard can talk to it, and it features some nice possibilities, a few LUTs, four comparators, a couple of timers and so on (part # SLG46826 if you care to have a look at it). It basically is an extremely small FPGA with some analog capabilities.

Since the SLG part has a configurable I2C address, the basic way to do what I need is to just add a 4 bits dip switch (or just coffe beans) and manually configure the boards each time I (re)build the matrix. Keep in mind that we will manufacture approximately 100 of the daughter boards, and have a team of people working with them, so it might actually happen that you pick a few from the drawer and need to reconfigure them.

I would like to come up with some sort of autodetection capabilities, I have been pondering on the problem for a few days now, and I did not come up with anything that is as good as I would like it to be.

There are of course a lot of constraints for the boards, here are the ones that I think are more limiting:

We are not pin limited on the north south east west connectors, you can assume you have many (10+) contacts available for the autodetect capabilities
We are pin limited on the SLG part, I can dedicate 6 or maybe even 8 pins to this, but of course fewer is better.
The motherboard is basically a big uC with I2C and some IOs, connected to a PC, so it can be as smart as needed
The daughter boards need to be perfectly identical
We will not need more than 16 daughter boards connected together, not necessarily in a square shape.
I want the motherboard to be able to control the whole grid from one single connector. It is acceptable that the connector is a specific one, e.g. a south connector as in the picture.

I have thought of resistor ladders configuration using the SLG comparators, but the comparators can only have fixed thresholds, shared between all the boards.

I have thought of being able to navigate the grid enabling the first board, then telling it to enable the one north, then e.g. go west.. And so on, but this has many corners and quirks and it looks like it needs to many pins on the SLG.

I have thought of a dead stupid row/col addressing, but this requires a lot of cabling, not acceptable.

As for now, the best option I have is the dip switch/coffe bean solution, but I am convinced there is a smart way to do this that I have not thought of.


texts: Interrupt-on-Change occurs twice on PIC16F1825

texts:
I am having a mind blowing misbehaviour in my PIC16F1825. Basically I am using pin 3 (RA4) to toggle a LED using an Interrupt-on-Change. Problem is, although it toggles the led whenever I press the button (which is externally pulled up), after a second, the LED toggles again, which means that the interrupt routine was called again, and it shouldn't, even though I clear the interrput flag.

Here's the code (only function IOconfig_portA() and toggleLed() matter for the problem at hand:

#include <stdio.h>
#include <stdlib.h>
#include <PIC16F1825.h>

char temp=0;

void interrupt toggleLed() {

    INTCONbits.GIE = 0;

    if(INTCONbits.IOCIF == 1) {
        temp = PORTA;
        INTCONbits.IOCIF = 0;
        LATC3 = ~LATC3;
        for (int i = 0; i < 100000; i++);
    }

    INTCONbits.GIE = 1;
}

void CLOCKconfig() {
    OSCCON  = 0x6A; //Sets the internal oscillator fosc = 4 MHz
    OSCSTAT = 0x00;
    OSCTUNE = 0x00;
}

void IOconfig_portA() {
    ANSELA = 0x00;           // All ports set as DIGITAL
    TRISAbits.TRISA4 = 1;    // Set as input
    //OPTION_REG &= 0x7F;    // Clear bit 7, to enable the weak pull-up
    //WPUA |= (1<<2);        // Enable the WPU for RA2
    CM1CON0 = 0x00;
    CM1CON1 = 0x00;
    IOCANbits.IOCAN4  = 1;  // Generate Interrupt on Negedge
    IOCAP  = 0x00;  // Disable Interrupt on Posedge
    INTCON = 0x88;    // Enable GIE and IoC interrupts
}

int main(int argc, char** argv) {

    TRISC = 0;

    CLOCKconfig();

    ANSELC &= 0x00; // All bits on port C are set to Digital I/O's
    TRISC  &= 0x00; // All bits on Port C are set to Outputs
    APFCON0 |= (1<<5); // Don't use special features on Pin RC3
    APFCON1 |= (1<<2); // Don't use special features on Pin RC3

    IOconfig_portA();

    LATC |= (1<<3);

    while(1) {

    }

    return (EXIT_SUCCESS);
}

Thanks in advance!


texts: Can the watchdog on an STM32F373 trigger a reset while the RESET pin is held high?

texts:
The reset pin on an STM32 chip is being pulled high by a Raspberry Pi Zero W in the field via GPIO pin BCM 17.

Will the watchdog on the STM32 be capable of triggering a reset while the pin is being pulled high?


texts: Cadence PCB designer How to extract the ground plane shape

texts:
how to extract the shape of the ground plane metal (only the gnd net) in dxf format from cadence PCB Designer?
Note that the ground plane is a autogenerated dynamic shape so if I move it I lose the shape of traces, vias and so on.


texts: If I have pulsed dc current going though an electromagnet, with the magnetic field mimic the current at higher pulsed dc frequencies?

texts: If I have pulsed dc current going though a copper wire electromagnet with no core , will the magnetic field mimic the current at higher pulsed dc frequencies?(such as ghz)


texts: PWM generator with adjustable duty cycle

texts: I'm designing a pwm generator comparing a saw-tooth signal with a DC signal. The saw tooth is applied on the non inverting input of the U3A, and it is compared with the DC signal that comes from the voltage divider. The problem is that I can't find a formula that relates the square wave that I'm getting at output, the saw tooth signal and the DC signal. Can someone help me figure out a formula so I can size the voltage divider?


texts: How to get more watts from a 1W amplifier?

texts:
I'm a newbie in the world of electronics, and I decided to build a 3 watt amplifier.
I searched arround the web and I found the following schematic for a 1W amplifier:

(source: hackaweek.com)
Note: Put a 2k resistor in between the ground and the emmiter if you want to prevent little distortion.
My questions are:

What is the "next stage output" used for?
Can I put there more amplifiers if I want to gain more watts?


texts: Inverting amplifier gain and input resistance

texts:
For the circuit of the inverting amplifier,  design a gain of -10 and an input resistance of \$100\$k\$\Omega\$. Give the values of \$R_1\$ and \$R_2\$.

Should I calculate the value of \$R_1\$ and \$R_2\$ by using \$-A_f = - R_f/R_1\$ and choose any value for \$R_1\$? What about the input resistance?


texts: Opening fail-safe electrical strike door with a spring

texts:
I have a 12V fail-safe electrical strike currently installed and working on a door, but I want it to open slightly when it is powered down, but a spring apparently won't do as my strikes keep themself locked if they have a constant force acting on them (so after unlocking, you either have to pull the door and the spring pushes it away, or push the door in place and the spring pushes it on you)
The question is: is there a way to open slightly the door with another type of electrical strike or is this kind of security on every one of them ? I need it to stay fail-safe though.

The other options I see are a solenoid pushing the door after the strike is opened, or a magnetic lock with a spring. Are there easier workarounds I didn't thought of ?


texts: Intermittent Power Selection with Mosfets

texts:
I'm designing a few boards that go in series with with each other.

simulate this circuit – Schematic created using CircuitLab

The PCB layout is the same for all, so PCBs with unpopulated PSUs will receive power from 5V rail, populated will provide its own power.

The ones that have a PSU(Vin to 5V) will supply 5V to the following boards.

The ones that do not have a PSU populated will use 5V from the former.

However the ones that have a PSU populated and also will receive 5V from former PSUs, and will have to cut the 5V input while allowing its PSU to supply the chain from this point on.

So we'll assume the CONSTANT 5V rail is permanently on at ideally 5V.

Will this power selection circuit correctly turn M2 on and M1 off whenever INTERMITTENT is on and vice-versa?

I have simulated this circuit on Circuit Lab and tweaked it a bit, have I missed something?

I have purposely put the FETs body diodes in this orientation (5V can be fed into the 5V rail but not into the INTERMITTENT PSU).

I have studied a few O-Rings but I'm not quite sure this will work.

p.s.: there is another higher voltage rail present for the PSU in all boards.

simulate this circuit


texts:
I need to choose a value for R1 to get the bulb shining. I was aiming to deliver 2 A current in there.

In the circuit below I am using NPN BJT transistor with beta value of 100 and built-in B-C potential value of 0.7 V.

My approach to figuring the resistance is

$$I_b=\frac{I_c}{\beta}=0.02 A$$

$$R_1=\frac{V_{CC}-V_{BE}}{I_B}=\frac{5-0.7}{0.02}=215 \Omega$$

However, in simulation, this resistance yields 1.87 A collector current.

P.S: R1 of 200 Ohms would yield 2 A collector current in simulation

Essentially, my question is why are my calculations of resistance are wrong/flawed?


texts: Why the earth attracts charge and where does the charge go when it goes into ground?

texts:
Self-explanatory question but to add what I know, by this I will also know if I am right or wrong.
I read somewhere that Earth is positively charged, but is not the state (whether positive/negative) of a body relative to the near body/object. If Earth is positively charged, why is it so? Is there any negative charge around it which helps Earth retain it's positive charge?

Also, what happens to charges that flow to the ground ?


texts:
I'm referring to one answer here

What if (power supply) was 24V, the VCC is 3v3 delayed by 1 second?

If you apply power then your (power loss detect) will be higher than the Vcc rail for 1 second? I don't imagine this to end up well.

In my mind i need an (and gate) that is activated by the CPU. But that will cost one more GPIO, so we can activate it from VCC itself.

However, is that and gate really required or there is better solution?


texts: CircuitLab simulation of 555 timer - OUT HIGH always delivering 5V irrespective of Vcc?

texts:
I've scratched together a design for a 555 timer based driver for an IR540 MOSFET. But in CircuitLab the simulator shows the 555's OUT voltage is always 5V when high, for Vcc ranges 3.3V through 24V. That doesn't make much sense to me.

simulate this circuit – Schematic created using CircuitLab

Does anyone know what the actual part for the 555 modeled by CircuitLab is? I've read that some 555s do have clamped output voltage, but most deliver Vcc - ~ 1.7V.

Is the modelling weird or am I just doing something dumb?

Crosslink: CircuitLab forum post

Related prior question


texts: Design a cascode BJT amplifier to achieve a specified voltage Gain

texts:
I have been asked to design a cascoded BJT amplifier with the given specifications

Voltage Gain = \$76 \  to\  84\  dB\$
Current Gain = \$66.5 \ to \ 73.5\ dB\$
Power Dissipation = \$ 3.5 \pm 5\% \ mW \$

However , I also have to adhere to the following rules :

Power supply rails available are\$ V_{dd} = 3.3V\$ and ground only.
Only one current source can be used in the design \$ I_{ref} = 50\mu A\$
Every bias voltage needed has to be generated by designing proper circuits.
Only one resistor of value around \$ 40k \Omega \$  can be used.
Output swing has to be atleast 80% of \$V_{dd} \$
Use the model BC108B for NPN and BC178B for PNP transistor.

To just start off , I designed a rough schematic as follows , not necessarily following the rule to keep only one voltage source :

By plotting the voltage transfer characteristics of BC108B transistor , I concluded that to remain in the active region , the \$ V_{be}\$ has to be between \$700mV \ and \ 900mV\$ , so i went with \$800 mV\$ , hoping both the NPN BJT's would be biased in the active region and give me a high voltage gain.
However , when I do the transient analysis , the gain comes out to be less than 1 , and also the bias current as \$ \approx 55 \mu A\$
I believe the reason for this small gain might be that the NPN transistors are actually not biased in the active region , but i am  not sure.
How do I get the desired voltage gain  as a starting point while at the same time satisfying the requirements mentioned before ?


texts:
So I want to build a micro-cooler (Cooling volume of 1l) to cool a block of tofu from 25C to -5C within 1-2 hours.
I'd like to do this with Peltier coolers and I wanted to get some insight from anyone that has attempted this before.
Using this heat load calculator https://tetech.com/cooling-assembly-and-heat-load-calculator/
I anticipate about 5W (assuming losses) of heat load to maintain my temperature differential.
Putting that load into this Peltier calculator https://tetech.com/peltier-thermoelectric-cooler-module-calculator/?mode=1&dtmax=70&heatLoad=5&hotSideTemp=30&coldSideTemp=-5&potted=0&emailsent=0
I'm given a few different models that should meet my requirements. Does this make sense or did I miss something?


texts:
I have two questions about reactive power.
1) I have read that the flow of reactive power is proportional to the magnitude of voltage difference between nodes. Could someone explain me this?
2) At the merchant vessel that i am working, if i increase the field excitation ( the current of generator's rotor ) the power factor increases. Why this happens?
Thank you.


texts: LM4890 amplifier and CR1616, how to improve power consumption?

texts:
I'm a hobbyst trying to design a simple circuit for amplifying the PWM audio output of an ATTINY85. I'm using an LM4890 (1W amp) and a 1W microspeaker. The problem comes when I supply 3V with a small coin cell, CR1616, which has a small capacity of 60mAh. The circuit works but the battery is drained fast. I checked the datasheet for the LM4890 but I'm still not sure how to calculate the resistor values for using less gain or reducing power consumption. I'm considering to add a regulator for the battery so the sound frequencies can be more stable. Any suggestions are highly appreciated. Below is the circuit:

LM4890 datasheet:
http://www.ti.com/lit/ds/symlink/lm4890.pdf


texts: What methods and equipments can I used to measure and record the current variation of CNC servo motor while machining.


texts: Use lithium ion car jumpstarter to charge netbook?

texts:
I have a Gooloo car jump starter pack.
https://www.amazon.ca/gp/product/B06X9R8QSY

Can I use it to charge a small Gateway Nav50 netbook?
What kind of adapter would I need?

I suppose I could use this:
https://www.amazon.ca/Cigarette-Lighter-Adaptor-Battery-portable/dp/B019LPOTVA
plus any DC to AC inverter, and then plug in the netbook's AC to DC wall wart adapter, but ideally I would like to plug the netbook's 12V input more directly to the 12V output of the Gooloo jumper pack.

Thanks for any ideas!


texts: Having trouble with light activated circuit.

texts:
R1 = 10K 1/4W Resistor

R2 = Photoresistor (any type)

R3 = 2M2 1/4W Resistor

R4 = 1M 1/4W Resistor

C1= 10µF 25V Electrolytic Capacitor

C2 = 100nF 63V Polyester Capacitor

D1 = 1N4148 75V 150mA Diode

IC1, IC2 = 7555 or TS555CN CMos Timer ICs

BZ1 = Piezo sounder (incorporating 3KHz oscillator)

B1 = 3V Battery (2 x 1.5V AA, AAA or smaller type Cells in series)

When a beam of light enters from the opening, or the fridge lamp lights, the photo resistor lowers its resistance (<2K) stopping C1 charging current. Therefore IC1, wired as an astable multivibrator, starts oscillating at a very low frequency and after a period of about 24 sec. its output pin (#3) goes high, enabling IC2.

This chip is also wired as an astable multivibrator, driving the Piezo sounder intermittently at about 5 times per second. The alarm is activated for about 17 sec. then stopped for the same time period and the cycle repeats until the fridge door closes.

So I'm trying to build this circuit and have a question
- Does this circuit start sounding the alarm 24 seconds after the light enters or just after? I don't quite understand it

and also how should I calculate to get the values 24 seconds and 17 seconds.

Thank you in advance.


texts:
I've been trying to find out what frequencies get filtered out by which type and capacity capacitors, but cannot find simple rules that say "type X, cap Y filters xxx (k/M)Hz - yyy (k/M)Hz". Yet everything I read seems to indicate this is common knowledge - or does everyone just use trial and error?
Who can help me out in providing some clarity on the matter?
Similar with ferrite beads/chokes. I know a big hunking choke helped me filter out the interference in my circuit, and have my eyes on some SMD-sized beads for on my small IC.
How do I know whether the big and the small choke both filter the same frequency?
An answer that tells me how to read a datasheet to find this out for myself is perfectly acceptable. By the way, I have poured over many a datasheet in the last few months.


texts: Write to sets of two bits in a register at a time in C

texts:
I am trying to set multiple values into a 32 bit register, and each value has 2 bits. Trying to come up with an elegant way to do this.

Write now I have something like this:

struct MuxRegister {
Uint16 PIN1:2;
Uint16 PIN2:2;
...
}

#define LED PIN1      (in a different file of course)
#define PWM      PIN2
#define Mux_GPIO 1         (value from 0-3 selects different options)
#define Mux_PWM  3
MuxRegister.LED = Mux_GPIO;
MuxRegister.PWM = Mux_PWM;
...

And I want to do something where I don't have to go through each MuxRegister.X and MuxRegister.Y for each of the 16 pins in the structure.

My idea was to do something like this:

#define BIT1 0x00000001
#define BIT2 0x00000002
#define BIT1 0x00000004
#define BIT2 0x00000008
#define LED (BIT1&&BIT2)
#define PWM (BIT3&&BIT4)
MuxRegister |= ((Mux_GPIO && LED) || (Mux_PWM && PWM) || ... ;

But there is no mechanism to preserve the spacing for the Mux code (values between 0 and 3) register beyond the very first position. As in, the value for Mux_PWM in this example is 0x00000003 but the value for PWM is 0x0000000C, and they don't interact at all since they aren't "overlapping".

Is there a mechanism with which to space out the values of the Mux codes so that they interact with the correct pin values? Sorry if I'm not explaining the question well. I don't have a lot of the correct terminology.


texts: Sensor data transmission without using a microcontroller?

texts:
What is the most traditional approach to getting sensor data onto a radio from an embedded device pcb that doesn’t utilize a microcontroller?

Up until now, we’ve been utilizing a convenient firmware on the radio that accesses discrete GPIO data directly wired to the radio’s IO and it automatically constructs everything on the UART for us. Now we need to load information that is not within the sampling capability of the old radio, but utilizes the same traditional UART for sending commands and streaming data.

I know there are probably standalone UART IC’s that I assume are serial setting configurable. Is this recommendable, or should I not waste my time? The benefits to no uC would be no need for new code and less strain on the PCB layout redesign, if we even have the space.

I would likely need bidirectional capability later.

Thanks


texts: Constant voltage term in model of diode with internal resistance

texts:
Ideal diode equation is $$V(I)=\eta V_T \mathrm{log}(\frac{I}{I_s}+1)$$
Model:

simulate this circuit – Schematic created using CircuitLab

If the diode has an internal resistance \$r\$, a more realistic model, valid in the region where the diode conduces is
$$V(I)=\eta V_T \mathrm{log}(\frac{I}{I_s}+1)+rI+V_0$$
Model:

simulate this circuit

Where \$V_0\$ is a constant voltage.

I think that \$V_0\$ is necessary for this model to work, but what does it actually represent?

What is exactly the role of \$V_0\$ in the model proposed?


texts: How can I detect an open analog input pin?

texts:
Many of the Renesas micros have built-in support to precharge or discharge the sampling cap on analog inputs to be able to detect when the external circuit is disconnected.  In the sample image, when the analog input circuit uses a pullup resistor, you can precharge the cap and if the external circuit is disconnected the input signal will remain high.  A similar thing can be done by discharging the cap if the input circuit uses a pulldown resistor.  These both assume that the circuit is interrupted at the black "X".

Is there a way to detect when the analog input circuit is interrupted at the red "X"?  Is it possible to detect a floating, or open, analog input pin?

If it helps, the port.pin in question can be reconfigured as a digital I/O to do [stuff] and returned to an analog input.


texts: I have replaced my car gearbox with one from a newer model. All works fine except for the speed sensor. The old one had a speed sensor with a toothed wheel and the new one comes with just the sensor. The sensor generates a small ac current. When I'm doing 50mph the cars speedo shows twice as much. I tried several resistors but the voltage remains the same. When the speedo shows 80 (actual speed 40) my multimeter shows around 0.8volt. Can you help me to lower the ac voltage coming from the speed sensor


texts: Can I pass a bit register as a function argument in Hi-Tech C compiler for PIC16?

texts:
Is there a way to pass a bit from a PIC's register as a function parameter?

Taking, for example, the PIC16F887, its registers (SFRs) and individual bits are defined as fallows in the corresponding header file (...\HI-TECH Software\PICC\9.80\include\pic16f887.h):

volatile       unsigned char    PORTB       @ 0x006;

volatile       bit  RB3     @ ((unsigned)&PORTB*8)+3;

How can I pass the RB3 bit as a parameter in a function so that it will allow me to call the function in this way:

setBitHigh (RB3);

What would be the function's prototype?

I'm using the HI-TECH C Compiler for PIC10/12/16 MCUs (PRO Mode) V9.80.

EDIT: The setBitHigh function is just a simplified example. I actually want to pass bits as parameters to more complex functions and to be able to choose at runtime which bits should the function use.


texts: What exactly is 1.x and 2.0 power scalar V/f control in VFDs?

texts:
These are terms that I have come across in multiple operating manuals for VFDs and usually, they just mention that it's used for variable torque applications. My doubt is "what exactly is it?" and is there a mathematical formula that I can use to derive this relation between voltage and frequency? I read some articles that say that this has something to do with affinity laws for pumps and fans, but am unable to understand how would one derive the V/f relationships using that.
Any help or even a general direction towards additional sources which could help me in this regard are appreciated. Thanks for your time!


texts: How to fix incorrect cutoff frequency using multiple feedback butterworth lowpass filter

texts: I designed a 6th order low pass Butterworth filter using multiple feedback topology (Fc = 500 Hz). But when I run it in LTSpice, the cutoff frequency is seen shifted far below to around 10Hz. Why is this happening and what can I do to fix it? Any comments or references to reading material are greatly appreciated. I apologize if I did not ask the question in the best format, first time on here.