texts: How to represent binary for differential and Menchester coding?

texts:
I have some questions with solution provided from random material, but I can't understand well.

Question 1:

I tried to represent binary for each block according to description in the picture above, is this correct? (where you see "? 1 1 1 0 0 0 0 ?") in terms of location I placed and the value of binary.

And also for 2 of "?"'s I drew at the end of each side, what would be good value to be in there? (i simply put "?" mark because I do not know binary for those 2 blocks)

================= END of Q1 =================

Question 2:

Similar question as question 1. I tried to represent binary for each block according to description in the picture above, is this correct? (where you see "0 0 0 ? 1 1 1 1") in terms of location I placed and the value of binary.

And also for "?" I drew around the mid point, what would be good value to be in there? (i simply put ? because I do not know binary for that block)

================= END of Q2 =================

Here are original images without my drawing in case if you need them to answer above questions:


texts:
I need to make a circuit that has a variant input between 0 and 9V.
It starts with 0V then once it reaches 9V a switch closes and if voltage drops back and reaches 5V the switch opens up and stays open until the voltage reaches 9V again.
So basically what's needed is to turn off a switch at a specific voltage (5V) and turn it On if and only if it reaches another voltage (9V)

Any idea how can this be done?
Maybe using Mosfets and Relays Since both have voltage controlled switches. But I can't seem to find a solution for this.

Regards,


texts: Can I use 5v 5A power supply for 5v 3A circuit

texts:
I have a dev board which came without power supply. As per the spec, it works on 5V 3A.
I have a spare power supply 5V 5A, can it be used here?

Will there be any issue?


texts: I Need Help With Volts And Powering LED Lights

texts:
I'm currently working on a science fair project, were I have to power a LED light bulb with potatoes. I can't find any websites that answer my 2 questions. Luckily I was able to find the answers to most of them. So i'll list them below and hopefully you can answer them.

How many volts does it take to power a 120 watt LED light.
How does a potato conduct electricity.


texts: Pairing to a module containing multiple Bluetooth units

texts:
I’m working on a project where a module is suppose to stream an audio signal to multiple receivers via Bluetooth. To be able to connect more than 7 units to this device, I thought of using three Bluetooth transmitters. But when I pair my Android phone to this device, I don’t want to have to select between the different Bluetooth units. I just want to be able to select the device and be paired with any of the available Bluetooth transmitter.
Any idea of how this is achieved?

Also, do you think it would be possible to stream an audio signal to multiple receivers via Bluetooth without pairing the Bluetooth units?


texts: RC oscillator and active bandpass Opamp filter

texts:
Here is my task:

Here is solution:

Although solution is there, I'm stuck. Firstly, how did they find transfer function? How did they treat diodes?


texts: Opamp current source stable in simulation but unstable on prototype

texts:
I've tried to build this opamp/mosfet current source, and been struggling to make it stable. When simulating the open-loop gain in PSpice. I've set it up like this, which should give Vout = -AB at the output of the opamp.

simulate this circuit – Schematic created using CircuitLab

And it looks to have a huge phase margin on the plot:

Which also shows if i step the input with a 1ns rise pulse, that it is very stable(measured at the output of the opamp):

But unfortunately it is very unstable on the prototype PCB that I made. The first picture is when the input voltage is 0, or below 10mV. The second picture is when I increase the voltage to around 70mV at the input:

Here is a picture of the PCB:

I could not route the 5V for the opamp on the single sided pcb, so I made a small jumper. At the input of the 5V there is a 10uF electrolytic and a 100nF ceramic as a bypass.
The green wire at the bottom is the input to the opamp. The other green wire is measurement at the gate of the opamp.
How can I simulate this circuit correctly?
How can I stop the oscillations in my circuit?
EDIT: I forgot to mention that i added C2 because the mosfet im using (ST p36ne06) has more input capacitance than this buz11 FET has.


texts: Why when i put a voltage through my photodiode its sensitivity doesn't change?

texts:
I have a photodiode that I want to experiment; the problem is that when no voltage is applied to the circuit
I get a voltage through the resistor of around 0.3V that change if I apply light. For any value that I put for the resistor I always get 0.3 volt.
The other thing is that for every voltage that I tried to put through into the circuit the measured voltage through the resistor is always the voltage that I put through the circuit plus the static voltage amount (the same 0.3 volt) so if I puts 5 volt through the circuit i will measure 5.3 volt through the resistor and it will do that for every value of resistor, so I'm not sure if it is normal since I don't really understand the need to put a voltage through the photodiode if the output current will always be the same
In conclusion :

When I don't put a voltage through the circuit the voltage measured through the resistor will always be the same for every value of the resistor; I will always get something near .3. I just remark that even if I don't put a resistor I will get this value so it make mes thinks i probably did  wiring error;

When I put a voltage through the circuit the value of the resistance will only change the initial voltage that I measure through the resistor but the maximum voltage will always be the voltage that I put through the circuit plus 0.3 V


texts: Extracting power supply for sub-circuit from an existing power supply

texts:
I'm trying to design a circuit that gets a power supply cable of 12V as input (that was connected directly to a Motherboard), and from this power supply I want to to add a branching for 3 connectors that should be connected to wires that pass ~2A and supply a power voltage to an extension that is intended to pass USB2 data. (not important for the question).
I built the following circuit as a solution, and I was wondering if this circuit makes sense in terms of power.

before adding my circuit (the part inside the red rectangle), VCC and GND were the supply voltage for a motherboard that consumes 60 [Watts], and the original wires passed 12[v] and 5[A].
after adding my circuit, I want to make connectors pass ~2A. (this is the limitation for the wires that should be connected there), and also to make the traces on my circuit wide enough to be able to pass ~10A for the motherboard eventually (as opposed to 5A that it used to get before).
according to my analysis, if I want to deliver 10 Amps to the motherboard, it means I need 16 amps to be at the input in order to satisfy KCL all the way until I reach the output, and that doesn't make sense to me since the power at the input would be 192 [watts].
I might not have understood my mission right for 100%, and I'm going to have a follow-up questions to my supervisor in order to have better understanding of the specifications, but before that I wanted to understand if my first intuition is right and see if I have some missing elements that should be considered.
I would be glad to get some clearance about the right process that should be taken to achieve these specifications.


texts: Altium 21 - how to configure multiple layers in schematic

texts:
While setting up some rules for a netclass, I wanted to prevent routing on top and bottom copper while allowing it on Inner1 and Inner2.
However, the rule dialog only has two layers available: top and bottom.
The PCB has many copper layers and I have tried back annotating but that did not seem to inform the schematic that more layers are available.
How do I get the extra layers into the net class "Routing Layers" dialog?


texts:
I had previously worked on Arduino but I think it was very simplified for the users. Now, I want to learn properly. I decided to begin learning ARM microcontroller. So, I bought LPC1114 DIP because I can do it on a breadboard. I didn't want to use any ready-made board. How do I proceed? Is there any tutorial for programming? I found some code and trying to learn from that. How do I program my microcontroller? I am kind of stuck here.

Edit: I decided to go for ARM after reading some comparisons. Since LPC1114 is 32 bit in comparison to 8 bit AVR, I thought learning ARM would be useful for larger projects.


texts: Should bus transceivers be used for a legacy M68SEC000?

texts:
I'm working on designing a simple "retro computer" based on the NXP 68SEC000.  The "SEC" variant (by NXP) is essentially a Motorola 68000 with a few differences.  Such as the inclusion of A0 and it's a static/CMOS version.

I'm also reading through the excellent Microprocessor System Design book by Alan Clements.  This book does not directly cover the 68SEC000 as it covers the "generic" 68000 from Motorola.

In the book, it references a minimal computer that has 74LS244 bus drivers between the address pins and other devices.  It also has 74LS245 bus transceivers between the data bus and other devices.

My understanding is that back then, many of these chips could not drive other components very well so these bus drivers were used to boost the outputs (forgive me, I'm a newbie when it comes to electrical engineering).

However, I have designed another computer in the past based on the 65C02 which doesn't need any drivers because it's modern, static and I assume just "stronger" in its ability to drive other components.  This computer proved to be very reliable and I have not seen the need for any drivers on it (yet).

I've tried to find reference designs that use the newer 68SEC000 but I cannot find anything.  My searches always leads me back to the generic Motorola 68000 (just like the book).

So my question is, is there any real benefit of using these drivers and transceivers on a new design that utilizes the 68SEC000?  Or, does the very nature of the CMOS/static design negate the need for them?

Some points of interest is that my design uses all new and modern parts (except for the 68SEC000).  My SRAM, UART's, etc. are all modern devices.

Thanks for any help.


texts: Calculating battery percentage using an Arduino

texts:
I'm doing a little project using a Lipoly charger and a 2500mAh 3.7V battery, both from Adafruit. I'm trying to display the percentage left on the battery. For that I'm using this little sketch :

long readVcc() {
  long result;
  // Read 1.1V reference against AVcc
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Convert
  while (bit_is_set(ADCSRA,ADSC));
  result = ADCL;
  result |= ADCH<<8;
  result = 1126400L / result; // Back-calculate AVcc in mV
  return result;
}

I saw on that page that the minimum voltage is 3.0V so I use that to get my values :

  float volt = (float)readVcc()/1000;
  float percent = ((volt-3)/0.7)*100;

When I display my values, it shows me that the percentage left is -4%. Should I worry or am I doing something wrong while calculating?


texts: How can these GPS/GPRS bike tracking locks be so power saving?

texts:
I am really puzzled by how these GPS/GPRS, solar-powered bicycle locks seem to be running on very little power. They are fitted with a tiny solar panel.

As you may know, these locks are popular these days with publicly shared bicycles like OFO, Mobike etc. As I understand, in principle they (continuously or very often) report their position to a server via GPRS connection. They may also need to poll the server frequently for commands (e.g. unlock the bike). In my knowledge all of this requires a lot of power. They are operated with an app, and as I understand for instance if you want to unlock from the app, data will be transmitted from the app to server, and from the server to the lock.

I am trying to DIY one myself in order to learn IoT.

I am basing my lock around the GPS/GPRS module SIM808 and base on my calculations (below) it require quite a huge rechargeable battery, and a huge solar panel to charge it. These commercial locks could be using other modules, but I would presume their power consumption should be more or less comparable since they use the same technology.

THESE ARE MY CALCULATIONS:

Let’s just put GPS aside since I see that GPRS alone is already enough puzzle for me.

I decided that to save power, my SIM808 will not maintain continuous communication with the server but rather to make a connection to the server (via TCP/HTTP to a PHP script) every 5 seconds to send data (GPS location for instance) and to receive data (e.g. command to unlock the bike).

Even with that interval, the module would need to make almost 20,000 data transfer sessions a day. Assuming that each session needs 1 second, then the total transmission time is about 5.55 hours a day. According to what I depicted from the datasheet of the SIM808, the module consumes around 0.48A during transmission (datasheet even says in some transmission bursts the current can be as high as 2A, but let’s just stick to 0.48A).

That requires a 2.7 Ah rechargeable battery to power the module for 24 hours. Of course, to account for winter days or when there is bad weather, I decide to triple the capacity of the battery to 9Ah (which I decide to use 12V 3S Li-ion since I have some around) so that the module can last about 3 days even without sun light.

Now for the solar panel to charge this 9Ah battery, according to the calculator here, I will need a 225W 12V solar panel, and with its size I think it should be mounted on a roof!

Could anyone please tell me where I may have gone wrong?

Thank you!

EDIT:
My calculations are wrong. The average power consumption should be < 1 Watt and a 10W solar panel is more than enough.

With clever power saving techniques, a 2W panel would be sufficient.


texts: As part of an ongoing project of computers ran by microcontrollers, one of my desktop models will overclock it's main MCU far past recommended operating frequency, since the first model isn't very fast. I'm thinking about using a Cortex M0 overclocked to about 100MHz, compared to the recommended 50MHz. I know that traditional CPUs perform faster at cooler temperatures, so would cooling the M0 to sub-zero temperatures using a thermoelectric module allow me to overclock it to what I want? Also, I would like to hear what you think about stability at these speeds.


texts: How can I calculate complex values in LTSpice?

texts:
I am trying to implement a circuit which contains some complex number of form:

$$
x + jy
$$

So my question is how to represent complex value while writing netlist in LTSPICE.


texts: Adapting an I2C FRAM chip to an SRAM-like parallel interface

texts: I have a project that requires a parallel interface non-volatile RAM. I had hoped to use an FRAM, however the only parallel FRAMs seem to much larger in capacity (and more importantly, price) than I need/want. On the serial side, things are much cheaper (even more so with EEPROMs). Digikey sells 8KiB I2C FRAMs for ~$1. That would be about perfect, were it not for the serial interface. What I'm curious about is whether there exist any kind of off-the-shelf solution for interfacing an I2C memory to a parallel interface


texts: Replacement for DC Tachogenerator in hydroelectric control system

texts:
I a mechanical engineer working at a mission hospital where we have a relatively new (2013) hydroelectric power plant. The turbine has a speed sensor (DC Tachogenerator) that provides a voltage to a control system to maintain constant RPM.

This Tachogenerator has been going through brushes rather quickly, and even with new brushes there is some fluctuation in the voltage (even though I know from the generator frequency that the system is running close to steady state). The frequency readout that receives input from the Tachogenerator will fluctuate around 3 Hz even though the generator frequency fluctuates under 0.5 Hz. With old brushes the reading is so poor the plant will overcompensate itself outside of the power quality parameters and shut down.

Our maintenance staff will clean the contacts of the rotor whenever they need to change the brushes. There is usually lots of carbon inside the housing.

I would like to know if we can replace this Tachogenerator with a more precise unit, preferably brushless. Long brush life is also important. We can't be shutting down several times per year to change brushes.

This resource is leading me to believe that a DC Tachogenerator is superior for our application. From my understanding an AC Tachogenerator would need a rectifier and capacitor to give a DC voltage with minimal ripple. However, the brushless nature of an alternator seems better to me.
http://www.polytechnichub.com/difference-ac-tachogenerator-dc-tachogenerator/

Please see the picture for details on the tachogenerator currently in use.


texts: Understanding the Pierce oscillator pi network

texts:
I've been looking at the Pierce oscillator and I'm unsure of the role played by the series caps to ground (the so-called pi network).

I've put together an image which attempts to explain my intuition (the 1's and 0's are a simplification; I understand that the crystal produces a sine wave).

I assume the action of the crystal - oscillating back and forth - causes the caps to charge and discharge and, crucially, produce the 180 degree phase shift at the inverter input pin.

The feedback "kick" is produced every half-cycle in response to C1 charging and is in-phase with the crystals current movement during this period.

Incidentally, as I understand it, the large resistor R1 is designed to put the inverter in a highly sensitive state (hovering around Vcc/2) where the slightest tip either way produces a large output (relatively speaking) in the opposite direction.  This is possible because an inverter output of Vcc could feed the input, in tiny increments though the feedback resistor, from 0 to just shy of Vcc/2 before it would "flip".  Then, of course, it would draw current from the input and so on until finally it settled at a balancing point around Vcc/2.

Is that more-or-less how it is?


texts: Power supply question in regards to powering 400 LEDs

texts:
I have WS2812B LED strips, that has 144 LEDs per meter. The ratings are:

43W/M .3W/LED
.06A per LED
Input Voltage of 5V DC

The recommended power supply stated by the website is 5V DC and 10A for 1 meter. If I wanted to use 400 LEDs that would be 2 7/9 meters. If I based my power supply on the recommendation, that would be around 5V DC and 30A, right?

The question is:

Is it possible to use a 12V battery, use a buck-down converter to 5V DC and 40A, and power the LED strip through the buck without doing any damage to the strips?

Thanks!


texts:
I'm trying to implement oversampling on a dsPIC33EP64GS502. According to the datasheet and the 12-Bit High-Speed, Multiple SARs A/D Converter (ADC) reference manual I have to configure the following bits to set the oversampling ratio:

I'm struggling to understand why a 2x and a 4x oversampling both provides the same 13-bit result, the same for the other ratios. AFAIK a 4x oversampling will increase the resolution by 1 bit, a 2x ratio should increase the resolution in 0.5 bits. Is this an error on the datasheet or am I misunderstanding something?


texts: One pulse to ON/OFF bistable latching relay

texts:
I've been trying to design a latching relay driver circuit, with using a push-button switch. Basically when the circuit is powered on, first press in push-button switch make the relay SET, then the second press will make the relay RESET state.

I've searched online and find this normal relay driving solution. But I couldn't figure out how to implement this into single coil and/or dual coil latching relay. I guess dual coil latching relay is easier to drive than the single coil one.

Any help is appreciated. (if possible please provide falstad simulation)


texts: Finding the bandwidth of second order lowpass filter

texts:
I have a lowpass filter with the transfer function \$H(s) = -\frac{3}{3s^2+s+3} \$. Converting it to standard form yields
$$H(s) = -\frac{1}{s^2+\frac{1}{3}s+1} $$
Comparing this to the standard equation \$\frac{\omega_n^2}{s^2+2\zeta\omega_n+\omega_n^2} \$ we see that
\$\omega_n = 1 \text{rad/s} \$ and \$\zeta=\frac{1}{6} \$. We can also see that the cut-off frequency is \$\omega_{cutoff} = 1\text{rad/s} \$.
I want to find the quality factor and bandwidth, and for that, I have found these two formulas given to us by our instructor (where d is \$\zeta \$):-

$$Q=\frac{1}{2\zeta} = \frac{1}{2/6} = 3 = 9.54\text{dB} $$
$$B=\frac{\omega_{cutoff}}{Q} = \frac{1 \text{rad/s}}{3} = \frac{1}{3}\text{rad/s} $$
However, when using MATLAB it tells me that the bandwidth is 1.52
>> H = -tf([0,1],[1,1/3,1])

H =

          -1
  ------------------
  s^2 + 0.3333 s + 1

Continuous-time transfer function.

>> bandwidth(H)

ans =

    1.5226

Can anyone spot a mistake I have made, and is the formula given by my instructor even valid?
One of the reasons I want to know the cutoff frequency is to draw a straight line approximation of the bode amplitude plot. I believe it should look like this, without the peak because it's an approximation:


texts: Analog multiplier using logarithmic and anti-logarithmic opamp issue

texts:
I'm trying to build a analog multiplier that takes in two voltages and produces the product of them. I have tried to simulate a circuit with finds the log of two voltages, sum them and then find the antilog of the result. It's required that I use this methods as it is part of the objectives in the project. However the antilog op amp stage saturates after the summing amp stage. This is the basic layout of the circuit:

 The test voltages at the input was at around 10mv at each input and the supply voltages of the op amps are 6 and -6 volts respectively.

Why does the anti-log amplifier saturate and how do I fix it?

Edit: I added a differential stage which I take the log of a separate voltage and now it works. But I still can't figure out why the original circuit is advertised as the basic log-antilog multiplier.


texts: How to compensate for op-amp offset voltage for AC current?

texts:
For simulation purposes, I know that one can setup a difference amplifier configuration and compensate for offsets for DC current by adding a voltage source on the inverting input, and adjusting it's value until output voltage is zero.

I tried the same thing for AC current, but it doesn't work. The offset is reduced a little bit, but it doesn't go below ~20uV RMS.

Basically I want to output a very small AC voltage from the differential amplifier, in the range of microvolts. Unfortunately, at that range the offset dominates the output.

How does one achieve 0V offset for AC current?


texts: In a time varying magnetic field why is the current flowing through a conducting wire connecting two points of a closed conducting loop zero?

texts:
In a Time Varying Magnetic Field like the one shown in the picture below,

if we connect two points on the closed conducting loop using a conducting wire, why is the current flowing zero ?

My textbook says something like "the emf and the potential drop across the connected points will cancel each other out". But I could not understand the meaning of the statement. Can someone please clarify ?


texts: Chip Design Computer Generated Files for Fabrication Process

texts: Could someone provide an overview of how the chip design files are used by the fabrication process? What I mean is once the design engineer(s) have completed the computer generated design blue print files for the fabrication process do these special files get read into the machines which fabricate the silicon or the wafer or the die? Can they be easily replaced with an updated version of the finished design files?


texts: I understand how D flip flop works but still not understand how it "store" a bit of data in a register in a running computer

texts:
I am reading this book "Computer Architecture and Organization" by Subrata Ghosal because I'm curious about how data is "stored" in the CPU register.
When I say "data is stored", I imagine something that allows me to:

Write data to it
As long as I don't rewrite, reading from it will return the last written data

And the book claims that the computer register allows that capability.
According to the book, a register can be made up of many clocked D flip flops, which are in turn can be made up of an S-R latch:

The D flip flop works like this:

When CLK is 0, Q doesn't change
When CLK is 1, D determines Q

Now a 4-bit register can be made up of 4 D flip flops:

I imagine this register is inside a RUNNING computer, then the CLK will alternate between 1 and 0 at specific interval. So my question involves this situation:

Supposed at point t0 in time: CLK is 1, I store in the third D flip flop the value 1 by setting the input to this flip flop to 1. Immediately after this, if I read from this flip flop, I will receive 1.
t1: CLK is 0: If I retrieve Q3, the value returned will be 1 -> I successfully retrieve the value I stored in this flip flop previously at t0.
t2: CLK is 1: Because now CLK is 1, Q3 will be depended on input of this flip flop. If at this point, the input is 1, then the value retrieved will be 0. But there's no guarantee that at this point, the input to this flip flop is 1. If the input is 0, I'll retrieve 0, which is not the value I previously stored at t0.

So it seems in order to retrieve the correct value I "stored" at a previous point in time, a necessary condition is that the correct input to the flip flop must also happen but there's nothing to guarantee that. This doesn't sound like "storing data" to me.
I must have misunderstood something but couldn't figure it out.


texts:
I have a transformer with 2 input leads and 3 output leads. I hooked up an LED to 2 of the output and put a dead AA battery on the input and the LED blinked for a second. I have no data on the transformer, but I am wondering if it is possible (and if so what is the schematic or instructions on how to do it) to put a low voltage oscillator before the transformer. I know how to work with 12 volts with a power MOSFET and a 555 timer, but my question is if this is possible with low voltage.
Any information is great.


texts:
I found this circuit, a voltage doubler with 555.

The duty cycle of the 555 is 50%.

Does changing the duty cycle of the 555 timer affect the voltage output like in boost converter? Or does it not change anything except the charging rate of the capacitor?


texts:
Recently I've faced with the term thickness-shear mode.

Then I googled the term above, but I couldn't find anything useful to learn.

What is thickness-shear mode technology?


texts: Is a linear voltage regulator necessary in AC to DC?

texts:
I was doing research on AC to DC power supplies and I came across a lot of schematics that use regulators like the one below:

credit: http://www.instructables.com/id/Make-a-simple-12-volt-power-supply/

Initially I drew out what I thought an AC to DC schematic would be and I basically did everything except including the LM7812 regulator.

Is it necessary or could someone get an equally good power supply by just using an effective transformer, bridge rectifier, and capacitors?

From the (Wiki) page it says the regulator is, "... conceptually an op amp with a relatively high output current capacity." Why this might be important, I do not know.

It seems to be the de facto standard in the AC to DC converter world and I would really like to know the importance of it.


texts: How can I detect a power outage with a microcontroller?

texts:
I have the following power supply configuration:
AC MAINS -> UPS -> 24V POWER SUPPLY -> 5V VOLTAGE REGULATOR -> PCB (microcontroller).
What's the best solution to detect the power outage on the mains with the microcontroller?
I also need to detect the zero-crossing so that I can control the speed of an AC motor.


texts:
I was reading a bachelor's thesis and it mentioned some technical details of a heated plate.

Part of the technical details:

  MK2b Dual Power Technical Details [7]
  ...
   Power Input: 12V or 24v
   Copper boardd holes
   Resistance between 1.0-1.2 Ω (12V) or 3-3.4Ω (24V)
   EPCOS 100k thermistor hole
   Functioning current PLA 8-9A, ABS 10-12A

[Accurate quotation above - typos are in the original]

The thesis I have is called :  Bachelor_Thesis_3D_Printer_Electronics_Design.pdf

The details are on page 18.

Did he make a mistake with the Functioning current?

From my very little knowledge in electronics, based on Ohm's law the current for 12V input is 10-12A and for 24V is 7.05-8A. And it doesn't matter what material is used PLA or ABS.

Or am I not calculating it properly?


texts: How to calculate the oscillator capacitor value for a switched capacitor (MAX7405)?

texts:
I would like to use an 8-order LPF switched capacitor: MAX7405 datasheet

The cut-off frequency can be set by simply connecting an external oscillator capacitor, Cosc.

I would like to design a 50Hz cut-off frequency but I have doubts on my calculation for the given formula in the datasheet.

Since I want to have a 50Hz fC, I needs the fCLK to be 5000Hz

From the given equation:

fOSC(kHz) = (K * 10^3) / Cosc; Cos in pF , K = 34 for max7405
5000(k) = (34 * 10^3) / ( C * 1pF)
5000 = 34 / ( C * 1pF)
C = 34 / 5nF
C = 6800M

By using the above equation, I calculated an extreme large capacitor with Mega value which is not reasonable.

Am I calculating it in the right way?


texts: Is there any difference between "induction" and "resonant" wireless energy transfer?

texts:
This article compares two systems for wireless energy transfer - one is by WiTricity and another is Bombardier PRIMOVE. I've read their descriptions thoroughly - to me they both look like resonant inductive coupling systems.

Yet the article says that WiTricity system uses resonance rather than electromagnetic induction and is more efficient because of that.

Is such comparison valid? Are there indeed "induction" and "resonance" wireless transfer systems or is it just the same thing being marketed differently?


texts: Unable to understand the details of step-down voltage regulator

texts:
I have currently purchased a 'Pololu 5V, 2.5A Step-Down Voltage Regulator D24V22F5' to regulate my 12v into 5v. This so far works fine!

The thing I'm wondering about it, and looking at the diagram and schematics of the device:

I need some help figuring out the PG and EN. From their website:

  The regulator is enabled by default: a 270 kΩ pull-up resistor on the
  board connects the EN pin to reverse-protected VIN. The EN pin can be
  driven low (under 1 V) to put the board into a low-power state. The
  quiescent current draw in this sleep mode is dominated by the current
  in the pull-up resistor from EN to VIN and by the reverse-voltage
  protection circuit, which altogether will draw between 5 µA and 10 µA
  per volt on VIN when EN is held low. If you do not need this feature,
  you should leave the EN pin disconnected.

  The “power good” indicator, PG, is an open-drain output that goes low
  when the regulator’s output voltage falls below around 85% of the
  nominal voltage and becomes high-impedance when the output voltage
  rises above around 90%. An external pull-up resistor is required to
  use this pin.

Ideally, and what I believe they are used for, I would like to attach 2 LED's onto the board (a green and a red) to light up if everything is OK or not. From what I can understand, can I just attach a red LED onto the EN and GND and it will light up when the voltage isn't sufficient, and can I attach an LED to PG and GND when so it will light up when the voltage is sufficient?


texts: capacitive proximity sensor - how does it work

texts:
I know 3d printers such as the i3 use a Capacitive proximity sensor to try compensate for the uneven surface of the print bed. for example this one seems to be popular
https://www.amazon.co.uk/gp/product/B00542U3M4/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

If am not mistaken a capacitor is formed with two plates and dialetric in this case glass.

Does this sensor work by forming a capacitor between the bed and the sensor i.e. the bed is one plate of the capacitor then the glass is the insulator and then the sensor itself is the other plate.


texts: 1200W, voltage and cycle converter 220 to110

texts:
I have bought a Joule sous vide immersion circulator  from USA. I want to use the device in India. I need to convert AC, 240V 50Hz to 110V 60Hz.
After reading the literature on the company's website it seems that just converting the voltage will not help, as the equipment design is such that it won't work properly.
Is there anything available that will convert both voltage and frequency simultaneously?
The device is 1100W, so please advise what can be done to use it without blowing it up.


texts: 3.3V very low power consumption buffer for sensor output

texts:
I'm designing a portable Ozone meter with an Arduino that read the data from the sensor and send it via LoRaWAN. I've found out this sensor that seems perfect for what I need.

My device runs at 3.3V and must have very limited current consumption. On the datasheet, I've read that the sensor consumption at 3V is 15uA which is perfect for me.

Now, as soon as the sensor has, besides the linear Vgas output, two other outputs (Vref and Vtemp) which, according to the datasheet, must be connected to a buffer before being read by the Arduino, I need a low power consumption buffer.

  NOTE: High impedance output requires a buffer to connect to any
  measurement device.

At this point, I was in search of a low power consumption buffer that works at 3.3V and I find this which is a multiplexer buffer with two input (perfect for me) and an output (so I can use only an analog read if I set up correctly my Arduino FW). On the datasheet, it also says that I can switch off the buffer (using 0V as Vcc) and the current absorbed by the buffer is very low (0.5uA) which is again perfect.

  Ioff is a feature that allows for powered-down conditions (VCC = 0 V).
  When VCC = 0 V, signals in the range from 0 V to 3.6 V can be applied
  to the inputs and outputs of the device. No damage occurs to the
  device under these conditions.

The only thing is that I can't find the current absorbed by the buffer while operating. Is it Icc=0.9uA?

As soon as I'm no expert in buffers, is there a better circuit/device to handle the sensor's outputs?


texts: Charging one capacitor with another capacitor in LTspice

texts:
I'm trying to simulate charging of one capacitor \$C_2\$ by another \$C_1\$ using LTspice. Following the derivations in this video, I found that in the end, both capacitors \$C_1\$ and \$C_2\$ should end up with a voltage of \$ \frac{C_1*V_0}{C_1 + C_2} \$, where \$V_0\$ is the voltage to which \$C_1\$ is initially charged. I have attached figures here showing my simulation and my result.

Initially, \$C_1\$ and \$C_2\$ are both at 0 V, as expected. After 10 ms, when S1 is closed, \$C_1\$ charges. With a time constant of 1 ms, \$C_1\$ charges fully in about 5 ms, as expected. After 20 ms, S2 is opened back up, and, as expected, \$C_2\$ retains its charge. (At this point, \$C_2\$ has already begun to charge slightly, which contradicts my expectations.) After 30 ms, when S2 is closed (while S1 is still open), I expect \$C_2\$ to charge up while \$C_1\$ discharges until they meet somewhere in the middle. However, I see a rapid drop in voltage on \$C_1\$ and a sharp increase and decrease in voltage on \$C_2\$.

I am not sure why this is but I have tried a couple of modifications. First I added a 1 k-ohm resistor in series with C2. The simulation and results are shown below. I'm not sure why how or why closing S2 causes the voltage on \$C_1\$ to change so rapidly (that too, for \$C_1\$, up to 16 V, which is well beyond the voltage Vin = 5V to which the capacitor was charged) and why the simulation abruptly stops displaying the voltage across \$C_2\$ at around 33 ms.

Finally, I decided to try a buffer amplifier instead of a resistor. The simulation and results are shown below. I'm again unable to explain why the voltages across \$C_1\$ and \$C_2\$ behave so erratically.

Could someone please explain what prevents the second capacitor from charging off the first?

Is there a way I could modify my simulation to get this to work?

This is actually a small part of a much larger circuit that I need to get working, so any help would be greatly appreciated.


texts:
I bought the Sparkfun's Uberboard a while back and I was trying to run the "Bootloader Tutorial" I followed all the instructions, got the FW.SFE file, but when the Uberboard resets it does not load the code. I got the following:

  SparkFun USB Bootloader v1.1 Boot up
  complete No USB Detected Failed
  Reading Header opening filesystem
  failed Root open "UART0 setup...ing
  firmware...

The "Failed reading header" what does it means? help, anyone? :S


texts: Bootloader jump to main application problem using STM32 with Keil Uvision

texts:
I am developing for the STM32F0 using Keil uVision.

I have a custom bootloader loaded running at address 0x08000000. I need the bootloader to jump to my main application which I flash at address 0x08003000. The ultimate goal is to allow remote updates of the main application. The bootloader code that jumps to the application is this:

__disable_irq();
JumpAddress = *(__IO uint32_t*) (APPLICATION_ADDRESS+4);
Jump_To_Application = (pFunction) JumpAddress;
__set_MSP(*(__IO uint32_t*) APPLICATION_ADDRESS);
Jump_To_Application();

I am getting a hard fault in the Jump_To_Application() line, with "Cannot access memory" message given by Keil.

Within Keil, I set the IROM1 start address to be 0x08003000 in my main application's project configuration. I feel like the problem lies in some further settings within Keil. For example, should IROM2 be set to anything? Should anything be adjusted from defaults in the Keil configuration within the bootloader project?

Does anyone have any recommendations?


texts:
Anybody knows the difference between these RF receivers?
I have a project and I am not able to work with RXB12.
It is not receiving my transmitter.


texts: Open-collector comparator with hysteresis and LED indicator at output

texts:
I am trying to choose the correct resistor values to make Vout go high when Vbatt falls below 18V and go low when Vbatt rises above 20V.  I've built the actual circuit and my measured values are 18.0V for the lower threshold and 19.6V for the high end. I used TI's reference design to choose the values for Rx, Ry, and Rh. Since the LM293 is open collector at the output, I read through the post here trying to account for the discrepancy between my measured upper threshold and my theoretical threshold. I believe D1 is the cause of my calculations being incorrect, but I am unsure how to analyze the circuit while accounting for it. Using the NSPW500BS model in LTspice for D1 gives me very accurate simulated values compared to the measured values of the actual circuit.

This circuit is a modification of an existing circuit, and I am restricted to only changing the five resistor values. How do I need to modify my calculations to achieve a desired range of hysteresis?

simulate this circuit – Schematic created using CircuitLab


texts: Designing a circuit using an LT1073 DC-DC Converter

texts:
I'm currently designing a circuit to convert a 24V  (±30%) to supply a 3,3V IC used to monitor currents. I need to use the LT1073 which has the following diagram.

The operations of the component and its applications are well-explained in the datasheet. According to the circuit example, I should place a 100uH inductor and a Schottky-Diode at the switch.
As far as my understanding goes, the Schottky-Diode is needed to block the discharge of current from going to the ground to allow the current to flow into the load. Is this correct?

This is how the circuit is supposed to be connected

According to the example, I need to put an inductor of 100uH. But what if this isn't possible and I need to pick a smaller inductor? What do I need to consider?

The datasheet mentions:

  To  operate  as  an  efficient  energy  transfer element, the inductor must fulfill three require-ments. First, the inductance must be low enough for the inductor to store adequate energy under the worst-case condition of minimum input voltage and switch ON time. The inductance must also be high enough so that maxi-mum current ratings of the LT1073 and inductor are not exceeded at the other worst-case condition of maximum input  voltage  and  ON  time. Additionally,  the  inductor  core must be able to store the required flux, i.e., it must not  saturate.

And then the datasheet goes on with some formulas that I can't really understand.

(1) Pl = (Vout + Vd - Vin)  * (IOut), where Vd is the diode drop(0.5V for IN5818 Schottky)

(2) PL = 1/2 * L * iPeak^2 *fOsc

These formulas raised a few questions:

Where does IOut flows?
How can I get fOsc?

I would really appreciate it if someone could give some tips or answers to my questions. Thanks in advance!


texts:
is XBee-PRO 900 compatible with XBee-PRO 900HP (S3B) 10K?

Are in general Xbee modules compatible between families?
I tried to change firmware but it didn't help.


texts:
I've recently gotten interested in electronics and so after doing some reading I've decided to have a go at building my own simple electronics circuit to control a 12V RGB LED Strip with wifi. I've chosen the ESP8266 chip, but at the moment I'm still focussing on getting it all connected.

I have a question and a problem:

About the MOSFETs:

I decided on mosfets after having read rants against the commonly used TIP120s, but for my application do I need to worry about the difference between standard mosfets and logic level mosfets?

I've found these two at local store: IRLZ44N(PBF?) and IRLB8721(PBF?) Apparently one is logic level and one's standard? Which do I use? They're the same price.

Problem with voltage input:

My LED Strip needs 12v, and the breakout board has a voltage regulator on board that takes in 4-6v. This means that I either hook up the strip directly to a 12v supply and find a way to step it down to 5v for the chip, or power the strip directly from 5v and then find a way to step up to 12v for the strip. Which way would you recommend? I assume stepping down is easier.

And with the chip drawing up to 500mA and the strip up to 1A, I don't think a linear regulator like a LM7805 would suffice; would a buck converter like the LM2596 work? Only thing that's stopping me is I've heard that due to the switching nature of buck converters they introduce a lot of noise and input voltage ripples to devices sharing the power supply. Do I need to worry about this if they're both connected to a 12v power supply and in the same enclosure?

EDIT2: Updated Circuit

EDIT1: Links for MOSFET datasheets as requested:

IRLB8721 - https://cdn-shop.adafruit.com/datasheets/irlb8721pbf.pdf

IRLZ44N - http://www.irf.com/product-info/datasheets/data/irlz44n.pdf


texts:
I made a small prototyping board where accelerometer data is read into a microprocessor, showing the data from the accelerometer after it is sampled, gives a very noisy signal. (50 mv peaks)

I had a similar problem before on a breadboard and switched to another breadboard/layout to resolve this but sadly didn't think any more of it. I think the problem is do to interference from the 5v power regulator or bluetooth module, however when using a oscilloscope I can't find the noisy signal anywhere on the board!

I would be greatly interested in any information which could lead me to find to source of the noise or solve it.

Edit1: The noise increases when the bluetooth module is sending data. So its almost certainly crosstalk or interference through gnd/vcc, any way to resolve this without resoldering?

Edit2: board layout http://imgur.com/bNLDdlz


texts:
I am making a Project with an Arduino driving a stepper motor with a driver board. USB will still be connected to send commands over serial.
EDIT:
I am building an EggBot driver board for my Arduino Uno which needs to be connected to my pc by USB for sending commands with the eggbot-software.
Here is my schematic https://imgur.com/a/nrF8RZ7)

Will I destroy my Laptops USB by having another power source connected to the same ground?

(I felt that I lacked general knowledge about DC power supplies and the resulting potentials. Therefore I tried to ask a more general question about AC to DC PSUs)

1. How different are the potentials between the neutral wire, the GND USB** and the GND PSU?

2. The power supply is a cheap one from amazon. So I assume there is no transformer and the 12V are not "floating". Is this safe to assume?

3. If both supplies are not floating, can there be a difference in potential between the GNDs?

4. If not, is there any workaround besides opto-isolation of logic?)

simulate this circuit – Schematic created using CircuitLab


texts: Measure impedance of rectifier using harmonic balance in ADS software

texts:
I am trying to use harmonic balance to find the impedance of the voltage double rectifier. After finding the impedance, I will use the impedance matching tool to find out the L matching.

As the pictures show, the frequency is 915MHz and power is 0dbm. I had got some result after simulation. Z0=50ohm, impedance of V1=Z0(4.108-j0.479), impedance of Vout=Z0(1-j7.163E-10).

But I am confused which point of impedance should be used to do impedance matching, V1 or Vout?


texts: How to connect solar panel to boost converter

texts:
Here I design a boost converter with 5 V input and 19.37 V output
and it is working very well when the source is DC battery
but when the source is a solar panel with also 5 V output I have no boost for the voltage did anyone know why this happens??

Here is the solar panel description:

Brand: GH Solar
Solar panel 10 W
Solar cell poly technology
Dimensions: 25.5 X 34.5 cm
Voltage at Pmax: 17.8 V
Current at Pmax: 0.57 A

Here the boost converter's input parameters

Vin:  5 V
RL:   100 Ω
Cout: 470 µF
Cin:  470 µF
L:    560 µH


texts:
I want to find a temperature sensor able to be used from -80 °C to 20 °C, measuring air temperature, with a potentially low pressure, reaching 1 kPa. Another constraint is that it should be as small as possible (a thermistor or TO-92 is small enough, though). Finally, its accuracy should be around 0.5 - 1 °C.

However, all the sensors I've found (mainly thermistors, and chips like the TI LMT87 or Tsic301) are only said to work in temperature above -50 °C.

What sensor could I use ?


texts: What makes a crystal oscillation to begin

texts:
I'm trying to understand how the Pierce oscillator works. Thanks to How does a Crystal work?, I've managed to understand almost all, but I'm still struggling to grasp, what causes the crystal to begin to oscillate at the very beginning? There's still no feedback AC coming into it.

Someone says that it's the "noise" causing the crystal to oscillate, but what noise? Audio noise? Electric noise coming from the circuit?

I would really appreciate if someone could help me to understand this "instant zero" of the Pierce oscillator.


texts: Single brushed DC motor driver not working when using step up voltage regulator

texts:
I'm using this Pololu single brushed drive to control a DC motor. Its voltage working range is from 4.5 to 28V and it works fine when I supply it with two 18650 batteries in series.
I want to make it to work with a single 18650 battery and since the maximum voltage would be 4.2V, I got this stepup to boost the voltage. However, it doesn't work at all. I re-checked several times and as soon as I supply the drive with the boost converter it stops working.
I'm quite new in the field of electronics and so not really sure if this normal or not. Is it possible to use stepup converters with drives such as the one I'm using, or this is something that will never work?
EDIT: add a schematic


texts: Do H-bridge configurations have any advantages over single MOSFET dc motor speed controller designs?

texts: I’m designing a simple dc motor speed controller that only needs to be driven in one direction and I’m wondering if an H-bridge configuration would have any advantages over a single or dual MOSFET control scheme besides being bidirectional. The motor in my project only needs to be driven in one direction but should be capable of dissipating power when spun in the other direction by the user - for example an electronic skateboard only needs to be driven in one direction but should also be able to spin (and dissipate power) in the other direction.


texts: Is a flyback diode necessary when no sensitive chips are used?

texts:
I have had a look through all the information available about flyback or snubber diodes in a relay system and was hoping to confirm if one is necessary in my circuit or not. All the info about why a flyback is necessary is due to the use of sensitive chips. My circuit is driving a pneumatic solenoid valve and has no chip on it; using two SPDT switchs to set a reset a latching relay.

Do I need the flyback diode that is currently included? To my mind the answer is no since I have no sensitive electronic parts.

Thanks!


texts:
I am trying to set up a pH sensor from Atlas Scientific using a Raspi3. I am using this Tutorial to set it up. I have set the sensor to I2C as the LED is blue. The circuit is shown here. I am now trying to run the i2cdetect -y 1 command, but when it prints out all the I2C ports are - instead of having 63 at its position. I think that I have connected my cables connected since they look the same as in the tutorial.

Any idea as to why the I2C sensor is not detected?

Thanks.


texts: Is there a way to avoid an infinite loop and reduce CPU power consumption when using PIC and timer0 interrupt?

texts:
I have made a simple program that runs on a P12F629 microcontroller using MikroC.

I need to run some time-critical tasks (e.g. increase internal clock, output data to LED matrix, ...).

Instead of a simple loop + Delay_ms() (which has its own set of problems), I use an interrupt:

void main()
{
    InitTimer0();
    while(1);
}

void InitTimer0()
{
   //setup timer0 interrupt
   //...
}

void Interrupt() //will be fired every x ms
{
   //perform some time-critical tasks
   //e.g. increase internal clock
   //...
}

The problem is a while loop consumes CPU cycles for nothing (and thus reduces battery life).

Is there a way to avoid this?

If I remove the while(1); call at the end of main(), the program runs exactly the same. Does it make a difference? Would adding a Delay_ms(1000) call inside the while loop help in reducing CPU stress?

In x86, I remember there is a halt instruction that halts the CPU until an external interrupt is fired. This would be perfect here. Is there such a thing in MikroC?


texts:
Assume that you have a couple of ideas that you think are good enough to prototype into demonstrable devices. What option would you take and why?

Option 1 - Build everything from scratch including designing and soldering the circuit, embedded software and finishing / packaging touches. Basically in this option, you do everything and don't source ready-made circuits from elsewhere. For e.g., you can easily get ready-to-use PCB's for power supplies, motor drivers and so on. Instead you build your own.

Option 2 - Figure out the common or readily available blocks in your schematics and source them from third parties. You work on only the parts that you think add value / novelty to your prototype (or one's that aren't readily available). These may include the electronics and/or the software.

There are obvious costing implications but I am asking to ignore those since they are easy to arrive at and analyze against. I am also not touching on obvious IP implications on getting stuff from 3rd parties - again assuming that these are taken care of legally. Also, please sensitize your answers to commercialization of these prototypes - that is, assume that these will be available as custom or off-the-shelf products in the future.

Rgds,

Sushrut.


texts:
For the above question I got the answers:

a. SUM = 0110 | C = 1001

b. SUM = 0100 | C = 1010

Are these answers correct and how is the overflow calculated?


texts: Difference in phase response between circuit simulation and MATLAB

texts:
I have the following low pass filter:

simulate this circuit – Schematic created using CircuitLab
When simulating through Circuitlab, I get the following phase response (I think you should be able to get this by simulating the linked circuit, If I embedded it correctly):

This looks consistent with what I directly calculated the phase response to be: \$ \phi = arctan(\frac{-2 \omega RC}{1-\omega ^2 (R C)^2}) \$. The full transfer function is \$ H(\omega) = \frac{1}{1- \omega ^2 (R C)^2 + 2 j \omega R C} \$. (Both resistors and capacitors are the same).
However if I use the bode plot function in MATLAB, I get the following phase response:

I'm given that the second plot is correct but I'm not sure why there's a difference in the simulation result and MATLAB result. Possibly I made some errors in setting up the simulation but I've used component values chosen by the solution to this design question.
I've also tried using calculators like Desmos to directly plot the phase response but it looks different from both the simulation and MATLAB result, but a bit more like the simulation.
Did I make an error in the transfer function, circuit simulation setup, etc?
MATLAB code:
R = 3900;
C = 0.0102*10^(-6);
H = tf([1],[R^2*C^2, 2*R*C, 1]);
bode(H);


texts:
I am reading "Intuitive IC Op Amps" by Frederiksen and getting stuck on one of the basic circuits. The book presents this image as a simple proxy for an op-amp.

Can someone help me understand a few things:

1) How is the Input biasing current and Output biasing current selected? What simple BJT circuits could realize these sources?

2) Why not replace Q3 with a diode?

3) What do D1 and D2 in the second stage do? Looks like they are trying to account for the diode drop of the Q6 and Q7 but I am not sure. What would happen if they weren't present? Why are 2 required?

4) What is Cc (compensation capacitor) doing? I vaguely understand that it's providing stability by pole separation. I can't get an intuitive grasp of what it's doing to the circuit, however.

5) Does anyone have a similar simplified image for a MOSFET implementation of a simple op-amp?


texts:
This is likely an obvious question for anyone with professional experience but I'm just a humble software engineer trying to fathom the mysteries of my oscilloscope...

I created a simple square wave using an ardunio, 20us on, 20us off. When I observe the wave with my scope, everything is as expected. When I bring a second wire in close proximity (but not physically touching) to the wire on which the square wave is generated and examine it on the scope, I observe that an electric field is generated on the wire which exhibits positive and negative polarities (the red line in the attached picture).

How can this be? If the square wave is only toggling a positive electric field on and off, how can the detected field on the second channel exhibit a negative polarity? I'm guessing that there's some sort of calibration or grounding effect required but I've grounded both probes...


texts: Design a sequence detector to detect 0110 or 0011

texts: I need to desing a sequence detector which detects 0110 or 0010, if any of this is received the output is logically correct, gives 1. My attempt so far. I would appreciate some advices, because I am not sure if it is correct. Thank you!


texts: Suggestion for a lack of light warning unit when in motion

texts:
I would like to build a small device that warns me, with sound and or a 'dash' lamp, that my headlight is off if the motorbike is moving. My challenge is it is under warranty, so I cannot in any way modify or attach to existing wiring. The unit must strictly only connect to the bike by something like silicone glue or Velcro.

I first though of an accelerometer in combination with an Arduino or something, but now I've wondering if a simply unit could be made with some kind of pendant switch, as I only need to detect some acceleration, not the magnitude of it.

The unit would be smallish, with a light sensor on one end, and a bright LED array on the front, to provide an iota of emergency visibility if the rider doesn't hear or see the warning for some reason.

The main gist of my question is, once the light detector and alarm is built, how do I enable it only when in motion?

BTW, the main use of this is for when a motorcyclist forgets to switch on his headlight during the day. It's quite easy to notice that it's off at night.


texts:
I have a system where there is a "master dimmer" (an 800W dimmer designed for household lighting). From that master dimmer, I have a few SSRs switching 40W incandescent light bulbs.

The idea being you can control the brightness of all of the lights with one dimmer.

However, the SSRs are only switching reliably when the dimmer is on full brightness, or set to very dim. Dimming mid way results in some lights just 'sticking' on.

Could the dimmer be messing with the zero crossing detection?

Any help would be much appreciated

Edit: this is the SSR being used


texts: Allow an analogue signal through unless a digital signal is present

texts:
Does a component exist that allows an analogue signal through until it receives a digital 1, then allows that digital 1 through? As an example:

Analogue sine wave going 0V to +5V is only input, output is the exact same sine wave
+5V DC input turned on
Output now becomes only +5V DC, ignoring the sine wave.
+5V DC input turned off
Output returns to sine wave

The digital signal won't be on all the time. When it is, I want it to override the analogue signal. My specific case is using four button/fader pairs.
I haven't found an accurate way to word it that might return actual components in Google. An Analogue OR Gate, perhaps?


texts: Sensing current upto 2A w/ high resolution

texts:
I'm trying to sense a current that will flow in a motor (current shouldn't exceed 2Amps), and I'd like to have a high resolution on this measurement.
I was hoping on using the ACS712, but it says the precision is 185mV/A.
Since the current in my applicaiton won't exceed 2A, it means 185*2 = 370mV (right?)

I'm using a STM32F4 with 12bit ADC which means with a Vref of 3.3V it's an increment each 0.8mV. So in the end I'll get a resolution of 463 steps.

Is there a way to get a higher resolution ? I don't really like the idea of a shunt resistor, maybe an amplificator could do the trick but will I be able to get a precise measurement ?

(iA is the measurement)

Btw, I'm trying to replace it with an ACS711 which operates on 3.3V but it'll give me only 110mV/A resolution

Here's the Vref+/- connection


texts: Unexpectedly drawing power over serial tx/rx? What to do?

texts:
I have this TTL-to-USB-serial device (supposedly from WINGONEER, who doesn't seem to have any documentation on how to use it):

https://www.amazon.com/gp/product/B06XY18XLL

I'm using it to hook up serial console on a system that has a 3.3V TTL serial debug connector with 4 pins: ground, tx rx, and a +3.3V supply. Since the USB adapter above produces 5V and 3.3V outputs on those pins, I left them unconnected. My expectation was that the adapter would only power up when the USB port is connected to a USB host, and that it would otherwise remain unpowered.

To my surprise, when I tried powering up the system it's connected to without the USB cable connected, the LEDs on the adapter lit and it seemed to be operational (power LED steady, activity LED flashing). Presumably it's drawing power over the RX line.

Is this potentially damaging?

I found the datasheet for the CP2102 chip and it indicates that the 3.3V can be configured as a supply or an output, but it seems to be configured as an output on this board. Would it be safe to hook it up?


texts:
so I have created a PCB with a lot of components on it, its a rather large PCB, roughly 18cm x 19 cm. A lot of the components' datasheets (things like Resistors, Switches, capacitors, relays, CAN controller/ transceiver) don't mention the thermal resistance of the components, nor does it include the power dissipation. Does anyone have suggestions to work around this? or generalizations / rules to estimate how much a PCB will heat up.
If it helps, some more information about my board,
Board lays horizontally, 1.6mm FR4 board
3oz/ft^2 thickness, 2 traces run 30A, 3 traces run 15A and 6 traces run 10A. They just run to a connector going off the board, only running through current sensor and relay.
But I am more interested for learning purposes, how thermal changed can be estimated with limited data?Also, do diodes heat up a lot typically and is it a concern for board temperature? because I have 9 small diodes it says their Thermal resistance is like 1000C/W 100mW dissipation


texts: Help with Wiring LED Parking Light/Turn Signal using manufactured Bolt LED

texts:
In my search to find the best way to complete this pet project on my truck, I found this site.  I've searched but as I am using a manufactured flush mounted bolt LED lighting unit I still have some questions on how best to set-up the wiring to get the LEDs to do what I want.

Background:  I found this Bolt LED when looking through a car forum the other day - http://www.oznium.com/led-bolt/tech  I've been trying to find something low-profile that has a simple and secure mechanism to hold it in place.  Based on the reviews, these LEDs seem to be pretty decent quality.  What I want to do is set-up 4 on each side of my truck along the toe plate of each running board and have them act as both additional parking lights and turn signals.  I had previously installed LED light bars and wired them up to my parking lamp and turn signal sources and ground for each side of the car.

I've attached how I think the wiring should be done.  I want to make sure I won't be harming the Bolt LEDs.  I saw one post talking about the 2 currents "adding together" when both the parking light and turn signal are on.  Do I need to be concerned with frying anything?  Will the 1N4001 Diode be sufficient for this application?  Should I assume a higher voltage than 12V?  Is wiring the Bolts in parallel the best method or would wiring them in series make more sense?

Thanks for any help you can provide!

Steve


texts:
I'm having some bass cancellation problems with my active subwoofer. It doesn't get along with my 2.0 system (different brands).

The subwoofer has a mono line input. I changed the polarity of the line cable going to the subwoofer and the bass came back to life.
The downside is I get a 50 Hz hum when the subwoofer volume is maxed and no sound is playing. With the normal cable no hum is present.
As I searched more on the internet, I found that some subwoofers come from factory with a phase shifter switch. I don't have that and I'm looking to build one myself. From my POV the problem doesn't seem to be that complicated, but the schematics I found for phase inverters seem to contradict me. I would have preferred a passive one, but I guess that's utopic...

The subwoofer is new and and opening to switch the driver's cables will void my warranty.


texts: How can you have immediates in the SUBLEQ one instruction computer?

texts: I'm thinking about making a SUBLEQ based CPU on FPGA. SUBLEQ (subtract and branch if less than or equal to zero) is an instruction which is universal. However, how can you have immediates/constants with this?


texts:
What's the best way to design a single activation falling edge detector?

I have a 3.3V power supply, and a separate GPIO signal that will begin toggling after power is applied. I need a signal to permanently toggle after the first falling edge, and then it should never toggle again no matter what the input does. This should be asynchronous and only depend on the input signal (or derivatives or maybe an inverted copy of the input signal).

simulate this circuit – Schematic created using CircuitLab

One thought I've had is to use a negative edge triggered DFF, with my INPUT signal as the DFF's CLK input, and PWR as the DFF DATA input. Then when INPUT toggles low, output toggles. The problem is next time the input toggles low, the output will change again, and I only want it to happen one time.

Any thoughts on how to accomplish this will be appreciated.


texts: Reverse Polarity Protection p-channel mosfet

texts:
I am trying to design a basic reverse-polarity protection circuit using LTspice but I am not sure what values to use. The input voltage is 12 V, 100 ohms resistor and a 10 V Zener diode.
What is the best P-channel MOSFET to use with this design? Any change to the current values is acceptable.
Reference circuit design:


texts: How to stabilize the magnetic levitation system?

texts:
I have asked similar question before also but want to try again - Not able to levitate magnet for magnetic levitation project

I followed everything from this project but still, the magnet is not levitating - https://www.hackster.io/jsirgado/magnet-levitation-with-arduino-eeeee4

The best I can do is to make the magnet jump up and down fast but it never levitates. Have tried changing PID setting from the project as aggressive and mild but still didn't achieve the final result.

I need advice from an expert to tell me what I am doing wrong here. All components are in good condition and 5v electromagnet is strong enough.

So what am I missing here?


texts: Will this 555 circuit prevent a car from disconnecting power to the radio when starting?

texts:
To start with I'm a little rusty with electronics, I haven't done much in 20 years and it was only a hobby back then.

In my car I have a head unit with a touch screen which relies on software to run it.

My problem is that it starts to load the software when you turn the key to accessories but when you go to start the car it cuts power to the head unit which hasn't finished loading the software. After the car has started (key returned to the on position) the power is restored to the head unit and it tries to load the software again.

This cut in power, I believe, is causing the head unit to malfunction, it messes with the software.

So I need to supply power to the unit when the key is turned to ACC or On position but held on while the engine starts.
After the engine has started the key will return to the On position and power the unit as normal.
When the car is turned off then the unit needs to turn off.

I was thinking of powering the unit through a relay wired direct to the battery and then using the signal from the ignition, in parallel with a timer, to trigger the relay.
If I use the loss of power when starting the engine to trigger the timer then the unit has already lost power and it would start loading again, so that would be of no use.

I tried to use the initial connection to power (when the key is first turned to ACC) to trigger the timer. If I am correct then with my circuit the timer is put into an endless 10 sec loop while the key is turned on and when the key is turned off only the timer powers the unit till the end of the time period. If the key is returned to the On or Acc before the end of the time period then the unit will stay on but if the ignition is turned off for longer than the time period then the timer stops and the unit turns off.

(This is also a diesel so needs the ignition to be turned on for a period of time before starting. I'm not sure if 10 secs is enough time but I don't think you can stretch it out further).

Can anybody verify if this circuit will work?
Is there a better way to do this?
If this is the best choice, is there anything wrong and what should I do to fix it?
(I wasn't sure if the 10k and 1k resistors connected to the base of the transistor were needed).


texts: Charging 250 volt capacitors without flash camera circuit

texts: I'm building a coil-gun in my high school engineering class and am having a little trouble charging the 5 250-volt, 1000 microfarad capacitors. Would it be possible to connect the wall to a voltage doubler, and then just hook that up to the capacitors(obviously with a fuse along the way for safety)?  I'll only be using the circuit under careful supervision, so reasonable danger is OK.


texts: Can a JFET replace a IGFET? (A 3N139 IGFET)

texts: it is my first question so please forgive my errors. I try to build the People Detector from Popular Electronics http://www.swtpc.com/mholley/PopularElectronics/Jun1968/PE_Jun_1968_pg28.jpg. The 3N139 is obsolete and i search to replace it. I found from a book the FET 3N128 again obsolete and for 3N128 is the JFET 2N3966 (i get it). For the Q2 i ll use a BC548B. My question is can a JFET with similar characteristics replace a MOSFET? Because https://www.electronics-tutorials.ws/transistor/tran_5.html mentions that; "It is essential that the Gate voltage is never positive since if it is all the channel current will flow to the Gate and not to the Source, the result is damage to the JFET".  From this i get that it cant replace for all applications the FET. Is it right? Does the Q2 used here as diode zener will protect it from this situation too?


texts: Voltage on ADC input when VDD is not connected. Dangerous? (ADS 1115)

texts:
I'm building a Raspberry Pi based system to monitor power output of a solar panel. I'm planning to use ADS1115 ADC. I sketched a simple circuit, but then I though of a potential problem.

It is possible that as some point the ADC will be connected to the solar panel, while the Raspberry Pi is either completely disconnected or not connected to power. The solar panel at this point can be producing voltage on the ADC input.

In my understanding the VDD pin of the ADC will be floating at this point.
The datasheet for the ADC says the maximum input voltage is VDD + 0.3V.
Do you think in such scenario the voltage from the solar panel can damage the ADC chip?

Thank you!

P.S: I googled the question a lot, but only found a topic on PIC built-in ADC, which said voltage on ADC input during PIC power-up can be a problem.

P.P.S: Sorry about the crudely drawn schematic.


texts: Using SMI to check speed of ethernet phy

texts:
I am trying to use the ethernet PHY which comes with my Digilent Nexus 4 DDR, a Microchip LAN8720A (datasheet).  I wrote a controller which lets me read and write values to the smi registers using the mdio and mdc signals.  Now I need to be able to tell if I am running in 10 Mbps or 100 Mbps mode.  Also whether I am in full or half duplex mode.  It looks like register 1 (BASIC STATUS REGISTER) would contain this information.  However, this register has bits 14-11 enabled.  These bits accoring to my spec mean...

14 - 100BASE-TX Full Duplex

13 - 100BASE-TX Half Duplex

12 - 10BASE-T Full Duplex

11 - 10BASE-T Half Duplex

I suppose this is telling me what the phy can do, and not the speed of the current link established by the auto negotiation.  There is also the auto negotiation advertisement register (reg 4) which has multiple modes enabled, and the link partner ability register (reg 5).  This two shows all four modes being lit up.

How can I tell what speed / duplex mode my link is?  Do I have to infer it by picking the intersection of the highest ability from the link partner ability register and auto negotiation advertisement register?


texts: Why doesn't this radio transmitter correctly transmit some songs?

texts:
I made transmitter from this question with some minor modifications (100 K pot for resistor between 8 and 7 and 22K for resistor between 7 and 6. 22 pF for the capacitor).
Here's the picture:

When transmitting this song, it is almost normally transmitted. On the other hand, when transmitting this song, almost nothing is audible. For example from 2:15 to 2:50 noting can be heard.

My home-brewed sound card oscilloscope (96 kHz, 16 bit) sees first song like this:

and the second like this:

If I'm right, on the second image only artifacts from the carrier wave can be seen (I'm running radio at 612 kHz. I guess that's OK, since it has range of about 5 cm).

I've heard such effects on radios with bad antennas before. What could be the technical explanation, or at least where could I start looking for it?

Just to be clear, the my question isn't about improving the transmitter, its about the effect I'm describing.


texts:
I want to build a digital dimmer for resistive Loads.
I have found this circuit for that:

The input voltage is 220VAC 50Hz.
The red box in the picture is for Zero Crossing Detection.

When the AC voltage crosses the zero, the Microcontroller will be interrupted an therefore detects the zero crossing. so you can reach to the required voltage by triggering the Triac after a specific Delay.Do you recommend this circuit? if so, please let me know if there is any IC to replace with the Red Box (shown in the picture) to detect the zero points of AC voltage (as my circuit should be as small as possible)?

P.S. As I need this circuit to reduce the consumed energy of Loads, the circuit itself must dissipate at most 5 watts.


texts: How would I switch between either of my two outputs into one input?

texts:
I am trying to design a circuit which will switch between two RGB outputs into a CRT TV's neck board. Each of the two outputs has three pins. I have tried using the 2N3906 PNP transistor, and it works but I have hit a wall with trying to get it to switch to a second output without interfering with the prior output. My design doesn't also seem correct as per where I have placed the resistors across the transistors according to examples online that I have found, but it seems to be working.

Notes:

The output voltages are ~1.2V at 40uA.
An ATMEGA328 is being used to control the logic.
Pin 3 of the ATMEGA328 is what currently controls the original AV RGB signal.
Pin 2 of the ATMEGA328 is what will be used to control the additional output.
The "IN CRT" labelled R1, G1 and B1 are the INPUT to the CRT neck board.
The "OUT IC" labelled R2, G2 and B2 is the AV RGB OUTPUT.

So, to avoid additional confusion I simply need to duplicate the transistor array so I can control a second output.


texts: What communication protocol does this pinout match? DATAP, DATAN, CLKP, CLKN, CLKSEL

texts:
I am trying to build a laser diode driver circuit using a part from Analog Devices. (The datasheet is here for your reference: http://www.autex.spb.su/ad/ADN2848.pdf)

It appears that there are 4 data inputs: DATAP, DATAN, CLKP, and CLKN. There also appears to be a clock select (CLKSEL) pin. I am relatively new to this sort of thing, so I'm not exactly sure how to interpret the data sheet to figure out what communication protocol to use when inputting data. Does anyone know what the protocol is, or have any thoughts/advice if not?

I also notice that the data sheet gives two values relevant to the data inputs: t setup and t hold. Are these relevant to the communication protocol that needs to be used?

Thank you!


texts: How to use L293D to spin HDD motor FAST?

texts:
Short version: I have a HDD motor I want to spin. I have the L293D chip and after hours of fiddling with code and timing, can only achieve 1200 RPM. How can I get more out of it?

Long version:
I have wanted to build the HDD pov clock for a long time, and finally got the L293D chips in the mail the other day.

after hours and hours of experimenting, the most I was able to get was about 1200RPM.. and even then, if I bump or slow the motor it would often stop and just chatter.

Here are a few key things I want to mention: I glued a small neodymium magnet onto the platter. I'm using a hall effect sensor, and I'm having some kind of magnetic interference. I have the 6 steps that it cycles through for each quarter-turn and when I write the 3 outputs, I first turn off an ENABLE pin, write all 3, then turn ON the ENABLE pin.  However, if I connect the enable pin [on the breadboard], it causes the hall effect sensor to trigger false, and instead of once per revolution, it triggers multiple times a rev [I'm assuming back-emf?].
So for now I just leave the enable pin alone, or tied to VCC, and the sensor works.

Oh and the other thing, I have 2 L293D's in parallel so to speak.  I hooked up 1, and it was getting too hot at ~500mA, so I put another one above it and put a jumper on each pin that was being used. shared the load, not quite even but it ran cooler.

that's all I can think of.. oh here's the full code: http://pastebin.com/8bQZWcFA
I switched from millisecond to microsecond delays so the comments of the code might not all be 100% correct.

the main things I'm wondering: is not shutting off the power before I switch polarities [due to interference I get when enabled] limiting my max speed? if so, if I get an infrared sensor what speed can I expect to gain?

and for the project I'm thinking of [http://www.ian.org/HD-Clock/ -- I haven't cut the slot in the plate yet] would  ~1200RPM be enough for POV? I'm thinking no, because it's 20 R/second, i.e. 20 FPS, and 24 FPS is what smooth animation looks like. [it would look choppy I guess?]


texts: Using crystal in LTspice (where to get values for RCL)?

texts:
I'd like to simulate a schematic in LTspice driven by a crystal. An capacitor representing the crytal (as a resonant circuit) however it needs some specific values. Is there a table of common values for crystals? I took a look in some datasheets but I think no sheet provides the values I need, here for example: http://www.jauch.de/ablage/med_00000876_1355237027_SS2-021112.pdf

Kind regards


texts: Is it ok to put a Triac in my communication path?

texts:
I want to protect a differential communications line from 24VAC.  This is an RS485 link running @ 115200.  I have legitimate signals @ +/-5V, but sometimes a foolish technician will hook up a 24VAC power line to it by accident.  This would ruin my RS485 transceiver (maximum voltage on inputs is +/- 14VDC).

I was considering putting a triac in the signal path.  The triac will shut off when a comparator detects rectified signal level over 24VDC.  2 zeners will clip the AC over-voltage @ 10V until the triac closes the path.  Is there a disadvantage to doing this?


texts: Finding the step response of a RLC circuit

texts:
For a homework problem, I am supposed to find the step response v(t) for the following circuit:

simulate this circuit – Schematic created using CircuitLab

Where the input is \$v_s(t) = 2u(t)\$, and the response \$v(t)\$ is the voltage across the capicator C1.

So, here's what I did.  I converted the circuit to the s-domain and constructed a transfer function:

$$\frac{V(s)}{V_s(s)}=\frac{\frac{1}{sC}}{R_1+\frac{1}{sC}||(R_2+sL)}$$

And then simplifying the function and solving for V(s):

$$V(s) = \frac{LCs^2+R_2Cs+1}{R_1LC^2s^3+(R_1R_2C^2+LC)s^2+(R_1C+R_2C)s} V_s(s)$$

Since the input is converted to \$\frac{2}{s}\$ in the s-domain:

$$V(s) = \frac{LCs^2+R_2Cs+1}{R_1LC^2s^3+(R_1R_2C^2+LC)s^2+(R_1C+R_2C)s} \frac{2}{s}$$

Which does not make sense because then the final value would be:

$$v(\infty)= \lim_{s \to 0} sV(s) = \infty$$

Which is impossible because you cannot have infinite voltage.  There has to be a limit.  What am I doing wrong here?


texts: How do you prevent solder paste from bleeding to nearby pads when using a solder stencil?

texts:
This is the first time I've done this but I've tried about ten times now:

That particular image is of the pads for an ESP-32. It's not a perfectly representative picture because the bridging isn't always that bad.

I followed this guide and in fact I ordered the stencil from JLCPCB but my results are messier. I think perhaps when the solder gets smooshed through the holes in the stencil it's going underneath the stencil to form the bridges. I've tried clamping the stencil to the board and putting a heavy weight on the stencil but it never comes out right.

Can you lead me to the light please. The LED light of course. ...which I will be able to see after I get this solder paste on the pads properly. Thank you!

EDIT - ended up getting it. Check the comments for more information.


texts: How can I create a serial bridge using two Bluetooth dongles?

texts:
I own two of the SparkFun BlueSmirf bluetooth modules and I would like to connect them to eachother - one as the master, and one as the slave.  It is easy to pair these together using a PC with Putty as the master, but some of the commands for the module require a carriage return to send a command.

How can I pair these bluetooth modules between two Arduinos without using a PC to send the carriage command signal from putty while the device is being configured?

I have thoroughly looked over the datasheet and command sheet for the module itself, but it does not include information of how to get past this problem.


texts:
I was unable to find an answer to this question, but feel free to link any additional threads I may have missed.
In my car, I have an aftermarket amp, and multiple HAM and public service radios. I would like design a circuit that would allow me to listen to music(source 1) through the stereo as loud as I want, but when audio is detected from one of the radios (Source 2), the music is muted and audio from the radios can be heard. Source 2 will likely need some sort of audio squelch circuit because the some amount of signal may come through the radio speakers even when there is no audio to listen to.  My understanding of circuits is very basic and I would like to learn more about this particular subject. I need help understanding how to trigger music muting based on audio from the radios, and the switching the audio.
Ideally, all radios would be connected to some sort of audio mixer through low level headphone or RCA input to 1 output to the audio switching device as source 2. The OEM head unit output (Source 1) to the amp is high level speaker wire. Input to the amp is currently high level speaker wire. The amp can accept low level RCA inputs, but the head unit requires high level output.
Could you please recommend a path to solving this problem? I lack the knowledge at this point of the correct research terms, but I would like to learn enough to design my own circuit.
Thank you very much! Solving this problem would be extremely helpful to me.
Cheers!


texts:
I'm looking for an alternative for a backup battery i'm planning to use.

PCB is powered by 24V DC power supply. I'm using a 3.3V LDO in combination with 3,6V battery to power mcu and other components (~20 mA):

It would be more convenient to use a supercap. The application only needs to run for a couple of seconds (@20mA). I'm worried about inrush current so my proposed solutions would be adding a resistor (1). However this will result in a bigger capacitor. Besides my Vsense line is no longer available to detect lost +24V supply:

So what do you think about using a supercap with series resistor (for charging) and a schottky diode for uncharching? +24V supply failure will be detected on the +24v side:


texts: In an intrinsic semiconductor, why don't electrons go out from both valence and conduction bands?

texts:
My textbook ("Electronic Principles" by Malvino and Bates) seems to suggest the free electrons in conduction band move left and reach the positive terminal of the battery. Does this mean electrons in valence band are not allowed to move left(hole moving right) and enter the positive terminal of the battery?

Similarly, it says the electrons from the negative terminal of the battery enter from the right directly into the valence band holes. Does this mean the electrons from the battery are not allowed to enter into the conduction band?

In summary: Electrons in an intrinsic semiconductor always leave from the conduction band and always enter from the valence band. This doesn't feel right. What am I missing?

EDIT: Saying electrons in the valence band are not free, so the battery cannot pull them doesn't make sense because of the following scenario: If a p-type semiconductor is connected across a battery, the battery's positive terminal has no problem attracting the electrons from valence band.


texts: What are the relations between analog transmission frequency and multipair cable types?

texts:
My question is a little theoretical about multipair cables.

I want to have some basic understanding about the relation between the multipair cable types and application frequency, length and and EMI effects.

Let's say we will use a 6-wire multipair cable. In the industry there are several types like:

Twisted shielded: Some types like CAT6 "each twisted pair has own shield" and also a main shield around all pairs. Here is an example:

(Source)

Only twisted: There are like LiYCY cables seems like they are twisted but they don't have "shield for each pair" and just one main shield around all wires. Some types don't even have the main shield:

(Source)

My question is: Is there a relation between having shield for each pair and frequency of the application? How can the reasons be explained? In other words how would one determine the cable type, if he knows the frequency of interest and the length of the transmission?

Maybe an example helps here: Let's say with a 6-wire cable you have to send balanced analog voltage signal with max 20Hz freq. along 100 meters outdoors. Would using shield for each pair in this case makes any extra advantage?

(I'm asking because a friend of mine told me twisted pairs and shielding is for high frequency signal transmission and using shielded twisted for each pair is an overkill.)


texts: How will an audio power amplifier output voltage behave when loaded?

texts:
If an audio power amplifier would power a 8 Ohm speaker through its proper(?) output and if the volume knob is set such that the amplifier outputs 8Vrms 440Hz sine wave across the speaker leads the power delivered to the speaker can be found roughly as if Im not wrong:

P = V^2/R = 64/8 = 8 Watt

But now if we add a parallel speaker the equivalent resistance will be 4 Ohm.

In this case will the amplifier act as a current source which will still output 8Vrms but double the current it sources? How about the typical effect of the mosfet power amplifier’s output impedance?


texts:
I recently purchased a DS3231 RTC module to use in one of my prototypes. Now that it is complete I would like to integrate the RTC directly into my PCB instead of using a plug in module. To that effect I have been trying to figure out the circuit using continuity testing on the module and the recommended circuit in the DS3231 datasheet. I have figured out all of it, except 2 things.

There are 2 capacitors in parallel connected between VCC and GND. There are no marking on them so how do I figure out their value?
There is a diode - resistor (210 ohm) pair between VCC and ground. Can't figure out the use of these since they are not in the manufacture suggested circuit diagram as well.

Any help is appreciated !

Edit: The diode in question can be seen in this closeup picture at the bottom side of the RTC here


texts: High side switching of a current source with 3.3V logic

texts:
I have built a Voltage Controlled Current Source that has no ON/OFF switch. This VCCS simply receives a voltage and outputs current to a DUT. The DUT is basically a high-power variable resistor (10 to 20 ohm).

So for example, if I give 100mV to the VCCS's input, it will try to supply 100mA to the DUT (regardless of its current resistance). And if I give 2V to the VCCS, I get 2A at the DUT (again, regardless of its resistance). So the VCCS is all fine and dandy.

Now, I need to implement a high-side switching between the VCCS and the DUT, that can be controlled by a 3.3V logic from an MCU. I tried to come up with some solution, and here is where I am currently stuck at:

And here is the result:

Can you please guide me to wire this circuit correctly? Also, I will appreciate it if you can name a NMOS and PMOS that can be used in this configuration. I have chosen the mos-es in the LTSpice arbitrarily.


texts: Help to identify 10-pin IC in a GPS unit

texts:
I am trying to repair a GPS unit. There was a zener diode (to56 PolyZen protection diode) which had blown off and I had replaced. This is part of the battery charging circuit I believe, as once I replaced it, the unit would power on and charged the battery for some time. Few weeks later the zener seemes like it has died again.

I found once I replace the zener again there is voltage at the battery terminal which slowly drops down but never comes back up so it seems something is killing it. The voltage drops gradually over 5 minuites

I’ve traced the output of the battery terminal to an IC like component that is next to this zener so have reason to believe it is faulty; but can’t figure out what it is.

The marking on the IC is D8 = 1K 70S

Would appreciate any insight as to what it could be.

It is the 10-Pin component in the middle, marked U750 on the board. The zener is slightly cut off the image next to C106.

Managed to find the component, it was RT9505GQW. Thanks to Remco Vink who pointed out the manufacturer was Ricktek. I emailed the company and got the correct part number. Many thanks to everyone for your help.

Hi I managed to replace the IC but didn't turn out to be the culprit. I keep getting 0.2v with the battery disconnected or battery voltage +0.2v when connected. I've found another component that is also connected directly to the battery and going to have a go at changing it. It is a 3 leg component with the marking "132V" situated next to the RT9505GQW I just replaced. Would really appreciate your help in finding this. Many thanks


texts: Finding Transfer Response (Simplifying resistor circuit)

texts:
I am trying to simplify the circuit shown in the image below, but i am not sure what to do with the resistor R3, as it is parallel to R2 but both are somehow connected to R4 (and so to ground).

How are the resistors connected (in series and parallel) so that I can find a transfer function?


texts: Eliminate effect of VBE in NPN transistor to maintain same gain ratio for a low dc input signal and at all operating voltages

texts:
Good day,
To monitor the current flowing through a varying resistor load across all supply voltages (8V to 20V DC), I am connecting in series, a small fixed sensing resistor and the drop across this sensing resistor is fed to the NPN transistor circuit for amplification.
The NPN transistor is operated with a gain Vout/Vin = -Rc/Re. Since the input voltage fed to the transistor is a fraction of the supply voltage, ranging from 0V to 2V max, I should be getting a linear amplification of Vout = -Vin*Rc/Rb and in theory I can make a linear function of vout based on supply voltage.
However, due to VBE of 0.7V, this linearity starts only when the Vin exceeds 0.7V and this offset is not desired as (0V to 0.7V) of Vin does not produce a change in Vout.
Is there a possibility of overcoming this problem of VBE? One option that I found in some posts is by using Germanium transistors with VBE of 0.2V but I believe they are pretty much obsolete.
Is there something I am missing or are there any other bright ideas that you could help me with?
Thanks in advance!


texts: What is the relation between Input Signals, Timebase-oscillator and Measurement time in Frequency counter?

texts:
An input signal of 2MHz is given to the frequency counter. The time base oscillator has the frequency of 1KHz. So, what I understood is (2MHz/1KHz) is shown in the display of 10 digits. ie 0000002000.

But if the measurement time(Tm) is given (ie 0.2sec)than time base osscillator is ignored and we use Tm. So,(2MHz/5Hz) is what is shown in the dispaly. ie. 0000400000


texts:
I recently bought an LTC3780 circuit from China to build a variable power supply.
I would also like to have voltage/current limit LED indicator there but every tutorial I found on the internet described the solution using different circuit than mine.

My question is: would it be possible to build such indicators when I am using LTC3780 and if so how complex would be that task?

Thank you for your answers.

P.S.: any hints how to proceed with that will be appreciate


texts: Has anyone ever heard of a circuit to automatically adjust the focusing anode on an electrostatically deflected CRT? Is there any way to even detect optimum focus other than by looking at the tube readout? I know on old CROs theres just a focus knob, but a lot has changed since then and I figured maybe something more modern would enable automatic focusing based on small current draw changes through electrodes or something like that. (?)


texts:
Please can anyone tell me what exactly is meant by reflecting of impedance in a transformer?

I do not know much about transformers, but I want to know about its uses and phenomena behind it.

I will be using a current transformer in my project to find out the impedance reflection. I do know the formula to find out how much impedance is being reflected, but do not understand the theoretical concept involved in it.


texts:
In a data sheet for a wireless transceiver I read

100 dB blocking immunity

what does this actually mean?


texts: Hi-Fi Stereo Amplifier gain regulation with potentiometer

texts:
This is my first question ever so please don't kill me :)

I have built a stereo hi-fi (end) amplifier 2x10W based on a IC TDA2009. I have bought it as a construction (learning) kit ready to solder.
Schematic:

(the pictures are from the manual that came with the kit, please don't mind the Czech headers)
Parameters for the circuit (from the manual) are:

Us power supply voltage: 8-28V (I use 9V power supply)
Peak output current Io (freq. >= 20Hz): 3.5A
...and more but IMHO (now) not important values

Now, everything worked great (although I had to replace the C8 capacitor, no idea why it was broken), so I decided I want to replace the R1 and R3 resistors with a potentiometer for variable gain (gain control). I bought stereo potentiometer, linear, 1kOhm, wired it up to R1s and R3s place (first pin ground, second and third pin to the PCB). When I turned the circuit on, the pot started smoking and burned.
If I get it right, I understand that the potentiometer couldn't handle the load when set to little resistance. I didn't really had a choice when selecting the pot as the one I used was the only stereo 1kOhm pot they had in the shop.
So I need to know:

Is my approach correct here? Can I replace the two resistors with a stereo pot?
Am I right thinking that the pot couldn't handle the current/load, or was it just a bad piece?
How do I calculate the power that can be on the resistance R1/R3?

Thank you for help!


texts: Correct charging current for lithium-ion batteries

texts:
I am trying to replace a lithium-ion battery for my Bose QuietComfort 35 headphones. I cannot find the datasheet for it. The battery is an AHB110520CPS (AHB110520) by Synergy. It is supposedly an "Advanced Hybrid Battery" which uses thinner materials than LiPo or something.

Its specs are 495mAh 3.7V, max 4.2V (I think).

I could not find a datasheet or anything about it on the net, including at archive.org. The battery model is probably about 2 years old and could be obsolete by now. The manufacturer's website has some AHBxxxxx.. battery models listed but not this one.

Other numbers found on it:

1ICR11/53
SYNERGY MH10048-E7
(chinese writing)

The battery has 3 wires labeled T (temperature), B+, and B-, so I don't think it has anything sophisticated inside it.

I would just replace it with a drone battery of similar capacity and voltage but I'm concerned about the charging current used for the battery. Do I have to find a battery with the same or more max charging current? I suppose I can measure the existing battery's charging current but what I'm curious about is what specs I need for the replacement battery in terms of charging current. I've read that lithium charging circuits are constant current/constant voltage (which is it?). So if the internal resistance of the battery is lower than the spec would there be a problem or not?


texts: Need a choke coil inductor for DC welder

texts:
Working on making an AC 225 volt welder into an AC/DC welder (225 volt AC and 125 volt DC).  I purchased bridge rectifier for 225 amp and 220 volts.  I am going to use two 3500 uF capacitors and a choke coil on the DC side.  I need to build a choke coil inductor to filter out high AC signals for it now.  Any ideas on how to construct this?

Can I use an iron core with nbr 4 insulated wire wrapped around it ?


texts: How to interface to a HyperRAM with a microcontroller

texts:
A couple of manufacturers have had this low pin count HyperBus interface now for a few years. It seems like finally there might be a way to get a few megabytes of RAM into a microcontroller project.

Has anybody had any success with interfacing to one of these SRAM chips with any common microcontroller?

For your reference, here's a datasheet of one 8 megabyte SRAM that uses this bus:
http://www.issi.com/WW/pdf/66-67WVH8M8ALL-BLL.pdf


texts:
I'm developing a new version of a 868MHz RF module based on Semtech SX1276 IC. I asking myself if I need to mount a SAW BPF on the RX path. On SX1276 semtech reference design there is a footprint for a SAW filter but is always replace by 0 Ohm jumper (U4 on this exemple) :

However I read in AN 1200.04 from Semtech :
“Semtech recommend that for most applications, provision be made for a SAW filter since ISM band
devices share frequency spectrum with GSM/GPRS which operates close to the 863 - 870 MHz;”
In EU this is true for GSM900 UL (876 to 915MHz) and also for LTE800 UL (832 to 862MHz).
As far as I know the advantage of SAW filter is that it will improve OoB (Out-of-band rejection) and mains drawbacks is additional costs and additional insertion loss. Tradoff between cost, "range" and reliability.
What is your opinion ?
Best regards


texts: How do I find the equivalent circuit of a compensated attenuator?

texts: I can not find the equivalent circuit due to the wire joining the middle of the resistor branch and the capacitor branch.