# All Questions

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### Calculating standby power or power consumption for switched mode power supply

Hi I'm new to electronics and I'm trying to design a standby power circuit that doesn't consume power any higher than 0.05W, the power supply will be a non-isolated switching regulator 24V in 3.3V out ...
3 views

### under-excited synchronous generator with leading power factor

Can an under-excited synchronous generator have a leading power factor below is the phasor diagram to explain it The Synchronous generator equivalent circuit is
9 views

### How does microwave oven work in grill and convection mode?

A microwave oven has a variety of modes, including micro, grill, convection, and combination. I read somewhere that microwave oven use coil heating for convection mode. In addition to dielectric ...
9 views

### What happens to an electric scooter if the battery is drained until 10% is left?

Is it going to have the same range as before after charging it or it will be shorter? If I charge the scooter above 50% in the next charge will the battery remain healthy?
16 views

### Does the number of turns in Turns Ratio matter in transformers?

Suppose we have two transformers with same turns ratio, $N_2/N_1$. First transformer $A$ is of $100:10$ and the second transformer $B$ is $1000:100$. Both have same turns ratio so both can ...
22 views

### I2C and SPI which interface to use when?

I have seen I2C and SPI interfaces being used with EEPROMs and other ICs. From an Hardware Perspective, what interface should be selected when ? One obvious reason I can find is that, I2C uses only 2 ...
10 views

### Pull-Up resistor for a 74LVC1G06 Inverter

As part of dual mode display port design, Pin13 goes to 74LVC1G06 inverter input (see U89): in case where I want to choose only HDMI I need to connect a pull-up to DP_0_PIN13. from wikipedia : "...
23 views

### Modern equivalent of the 6402 UART?

The 6402 UART seems to be relatively unavailable or at least at the verge of discontinuance. Is there a modern version of this UART that behaves in a similar way?
15 views

### Current sensor problem

I'm using INA219 to read the hold system current like the schematic The problem line in the DC-DC converter. When I use IC MP2315 DC-DC converter, INA219 seem like just read the off period of PWM ...
19 views

### ESP32 based device schematic review

I am building an IoT device with ESP32 WROOM as a host MCU. I have already made two test PCB with it, and show somewhat unstable behavior. The issues are; It seems like USB-UART is unstable. ...
63 views

### Why is this meter giving different readings depending on its orientation?

My newly-restored (re-capped) 1950s vacuum tube voltmeter is now operational...but there's one further issue. The meter gives correct readings when lying on its back, but when oriented vertically- as ...
50 views

### How to calculate the frequency and duty cycle from excel sheet?

I would like to ask for opinions and suggestions about finding a square wave frequency and duty cycle. I have an excel file that contains 4000 samples whose sampling frequency was 4Mhz or 0.25uS time ...
55 views

### What is the capacitor in this typical application for?

I've been looking at the TC1252 voltage regulator (datasheet available here), but can't figure out what the purpose of the second capacitor (connected between VOUT and GND) in the typical application ...
22 views

### Crystal Oscillator for STM32F407 with LAN8720

I'm planning to build a custom board with STM32F407 chip for a system where I also need Ethernet connectivity. I'm planning to connect this board to a LAN8720 with breakout board from Smart ...
24 views

### Building intuition on the behavior of inductors and capacitors with both voltage and current

I understand that an inductor cannot change current instantaneously, however I am not sure how that relates to the voltage. In a high pass RL circuit, for example, I know that the inductor presents a ...
36 views

### How does pulsing current through a better conductor generate more heat?

We are pulsing 20A, 12V current for electrolysis through a 6% KOH solution between two steel plates. Because of steel shortages, we have switched to a steel plate that is very slightly thicker. We ...
42 views

### Complementary mosfet to 2N7000?

I found this post: Is there a popular small signal PFET equivalent to NFETs 2N7000 or BS170? It is stated there that BS250 can be used as complementary to 2N7000. In my local stores I can not find ...
17 views

### ESP8266 Button Latch - Always On

I'm trying to build the following: Press the button shortly, the ESP8285 should turn on. GPIO16 can then be used to turn off the circuit. The button press should latch the power on. The problem: When ...
27 views

### Flip Flop from NAND gates

I'm currently trying to build a 4 bit LED counter that uses flip flops made from NAND gates. I'm using the CD4011BE IC and I'm having a bit of trouble figuring out how to build the flip flops. I've ...
37 views

### Why do crystals have 0° phase shift at series resonance?

I am trying to understand the inner workings of crystal oscillators, but I do not understand why the current has 0° phase shift at series resonance. To my knowledge this is the equivalent circuit for ...
65 views

### Why don't mass-produced LED chips burn out right away?

In a previous post, I was trying to determine if one of the pre-assembled 300mA LED chips shown below could be rigged up with parallel and series resistors to be correctly powered by a 350mA CC power ...
40 views

### What's the name of this DC-DC topology?

I was helping some friends that wanted to add a light load to a DC power rail in an industrial installation. The voltage to this rail comes from an array of voltage sources, with one voltage source ...
33 views

### Why does the led turn on in the following circuit?

So i have connected a transistor as shown below where the base of the transistor is connected to the negative of the power source and the emitter is connected to the negative side of an led and the ...
45 views

### Why TL071 Does'nt Act As a Comparator?

I am trying to obtain a square wave using a comparator and a sine wave signal. Sine wave has adjustable peak to peak amplitude with +10/-10 volts as limits. TL071 runs with +12/-12 volts. Sine wave ...
20 views

### How to improve this bypass switch from floating/differential to grounded/single-ended with just one DPDT?

This is for use in guitar onboard active electronics. (i.e. battery powered, installed in the guitar.) I want to be able to switch between: Differential input (to Op Amp circuit) with pickup coil ...
64 views

### Why is this 3-way speaker wired this way?

I found a service manual of a pair of 3-way speakers that were part of a mini integrated stereo system. These are Sony SS-H77 speakers, which have served me very well back in the day. Looking at the ...
26 views

### Shouldn't the Thevenin equivalent have the same behavior (regarding the transfer function) as the circuit it's derived from?

I am new to electronics and I have a little trouble applying the basics I learnt so far. My problem is basically that I don't understand why we consider the second circuit below as the Thevenin ...
54 views

### How to turn 4 LEDs on one-by-one using a potentiometer (without programmable device)

I am trying to build a simple circuit that contains 4 LEDs. All LEDs (except for the first) would initially be off. I would then like to use a potentiometer to turn on the LEDs one-by-one. For example,...
55 views

### If I put an L298N between a 12V source and a 100W DC fan, what will happen?

The L298N stepper motor controller module has a driving current of 2A ("MAX single bridge", not sure what that means) and a maximum power of 25W. I don't understand what those power limits ...
27 views

### Toroid core transformer: consequences of doubling the number of turns

In a 2N3904 common emitter RF amplifier circuit that I am building, the designer uses a FT37-43 miniature core with an 8 turns primary : 2 turns secondary ratio to couple to the next stage. I ...
34 views

Real-time electricity usage in Texas is graphed by ERCOT, the Electric Reliability Council of Texas. Today's graph can be found here, with a screen-grab below: Note the difference between the lines ...
15 views

### Debugging communication with HC-05 bluetooth module

As far as I am aware, sending an HC-05 bluetooth module the binary for "AT\r\n" via UART with a baud rate of 9600 bits/s should elicit a response of "OK" back from the module. ...
84 views

### TL071 does not integrate my sine wave

I want to make a homemade function generator. I used a Wien-bridge oscillator with a UA741 to produce the sine wave, amplify it with another UA741 because it has quite low amplitude, then integrate it ...
31 views

### Mains Power Supply for STM32F407 chip

I'm planning to build/design my own STM32F407 chip based board for controlling a DIY audio amplifier. I will have attached to this board some devices like LAN8720, SSD1309 based display and 3/4 LEDs. ...
31 views

### Understanding the Schmitt trigger circuit using CMOS inverters

This is the circuit I'm trying to understand: What I understand: Clearly, whenever $V_{out}$ is low $M_{3}$ is off and the strength of $M_{2}$ and $M_{4}$ surpasses that of $M_{1}$ so the ...
31 views

### Connecting a 48 V, 12.5 Ah 2C Li-Ion battery (or two in parallel) to a 48 V, 1000 W motor and 1000 W, 40 A controller

I am trying to build an E-Bike that uses a 48 V, 1000 W BLDC Motor with rated current of 35 amps and peak current of 60 amps. I have a Li-Ion battery 48 V, 12.5 Ah with continuous discharge current of ...
85 views

### Why does a 12V 2A adapter measure only 0.358A on a multimeter?

I assume that the multimeter should read 2A, why is it only 0.358A? If this is how it is supposed to be, why? If I add a load, how do I measure that this load is being drawn, does the multimeter need ...
22 views

### How do I use the 'generate' keyword in Verilog

I am trying to create a basic example of the use of the 'generate' keyword in Verilog, in EDA Playground. However, it gives me errors that I don't understand. ...
38 views

### Input diodes on op amp

I wanted to make sure I had the correct view on this circuit. From my understanding D1 and D2 are input protection diodes that clip the input to prevent any large voltage differences to damage the ...
20 views

### Designing Differential amplifier with differential output

I have done calculations for designing a differential amplifier (DA) with differential output. I simulate (using cadence ) the DA with the calculated values and perform the DC analysis of the circuit ...
36 views

### All ingredients for DC motor power electronics design

I'm trying to sum up all the ingredients for motor control power electronics: High Inrush current circuit – The short circuit and starting current rating of the DC motor is 7 times higher than the ...
19 views

### How do terminate the coax shield of AC coupled LVDS signal? (isolated grounds)

I have an LVDS clock signal that goes to several PCB cards. Frequency: 100Hz --> 20MHz I am going to use a fan out IC to supply each card with it's own buffered CLK signal; I am not going do a '...
28 views

### Antenna matching - semi-rigid cable (impact of length & diameter)

I'm new to antenna matching and would like to understand the effect of length on the return/insersion loss on an semi-rigid SMA connector. This is the datasheet of the connector I am using. This ...
15 views

### ESD pins of CM1624

I am considering to design SD interface with a CPU. For ESD and EMI, there are some ICs that can prevent these issues with RLC filter and TVS diodes such as CM1624. What I am wondering about is that ...
24 views

### Low Current (<500mA) Transient Current Suppression Methodologies

I am looking into possible methods of protecting against small current transients for use with a laser module and am having trouble finding information, partly because I am unsure what exactly to be ...
39 views

### How to know when USB-C is disconnected without measuring current?

I need an alarm to go off when a USB-C connector is disconnected from a phone. Need to do this without measuring current or voltage. So basically integrating it another way into hardware circuit ...
72 views

### 1 input 2 outputs logic

I have a system that can only supply very low current > 10mA at 12v. It has one output that will pull high or low depending on if it is powered on or not. I have another device I would like to ...
26 views

### Op Amp Input noise and bias current relation with input quiscient current

I am trying to understand how varying the input differential pair quiscient current in an op amp will affect its: a) input bias current, b) input current noise, c) input voltage noise. Based on ...